What are sharks immune of?
542071
It is indeed a myth that sharks cannot get cancer, but their rather "simple" immune system works surprisingly well (think for example that sharks during mating bite - usually the male bites the female - leaving the partner with deep lacerations of up to two inches and five or six inches long, which after about two months have healed without any scarring).  One of the reasons we thought elasmobranchs (sharks, skates and rays) cannot get cancer was that we had never seen one that had.  But since then, sharks with tumors have been found and another myth was debunked.\n\nNow, in experiments elasmobranchs have shown tremendous resistence to toxins that would be highly cancerogenic in humans.  In the late 80s, Carl Luer of the Mote Marine Labs tested aflatoxin B1 on nurse sharks and found that they metabolized it differently from us (it is actually the metabolite we produce that gives us cancer).  In other words, a number of pro-cancerous substances in humans are not necessarily affecting elasmobranchs.
1042893
The ones that actually adhere to the sharks are remoras. They're fishes belonging to order Perciformes, family Echeneidae, and they have a dorsal sucking disk with which they attach to sharks , but also to other bony fishes, turtles or marine mammals. These fish clean their "host" and feed on their leftovers.\nThis is what a remora looks like:\nhttp://www.amonline.net.au/fishes/fishfacts/images/enaucsh2.jpg\n\nThe other, more typical-looking fish with dark and light vertical stripes, are pilotfish. These also belong to order Perciformes, but to a different family, the Carangidae. Their scientific name is Naucrates ductor. They were called "pilotfish" because of the belief that they "guided" sharks. Actually, they're semi-obligate commensals of sharks, rays, other bony fishes and turtles, which means that they depend very much on them to feed on their leftovers.\nThis is what a pilotfish looks like:\nhttp://www.horta.uac.pt/imagdop/Servicos/Naucrates_ductor/035_s410_31.jpg
29544
Sharks have two senses that many animals do not have:\n\nElectroreception: The Ampullae of Lorenzini are small pits in the head that detect electricity. The shark has the greatest electricity sensitivity known in all animals. This sense is used to find prey hidden in sand in bottom feeding sharks, by detecting the nerve impulses. It is this sense that sometimes confuses a shark into attacking a boat: when the metal interacts with salt water, sharks can detect the resultant electrical charge from over one mile away. \nLateral line - This system is found in most fishes, including sharks. It is used to detect motion or 'sound' in the water. The shark uses this to detect other organisms moving, especially wounded fish. The shark can 'hear' frequencies in the range of 25 to 50 Hz using this sense.\n\nHOW TO SWIM WITH SHARKS: A PRIMER \nVoltaire Cousteau\n\n\n--------------------------------------------------------------------------------\n\nForward\n\nActually, nobody wants to swim with sharks. It is not an acknowledged sport and it is neither enjoyable nor exhilarating. These instructions are written primarily for the benefit of those, who, by virtue of their occupation, find they must swim and find that the water is infested with sharks.\n\nIt is of obvious importance to learn that the waters are shark infested before commencing to swim. It is safe to say that this initial determination has already been made. If the waters were infested, the naïve swimmer is by now probably beyond help; at the very least, he has doubtless lost any interest in learning how to swim with sharks.\n\nFinally, swimming with sharks is like any other skill: It cannot be learned from books alone; the novice must practice in order to develop the skill. The following rules simply set forth the fundamental principles which, if followed will make it possible to survive while becoming expert through practice.\n\nRules\n\nAssume all unidentified fish are sharks. Not all sharks look like sharks, and some fish that are not sharks sometimes act like sharks. Unless you have witnessed docile behavior in the presence of shed blood on more than one occasion, it is best to assume an unknown species is a shark. Inexperienced swimmers have been badly mangled by assuming that docile behavior in the absence of blood indicates that the fish is not a shark. \nDo not bleed. It is a cardinal principle that if you are injured, either by accident or by intent, you must not bleed. Experience shows that bleeding prompts an even more aggressive attack and will often provoke the participation of sharks that are uninvolved or, as noted above, are usually docile. \nAdmittedly, it is difficult not to bleed when injured. Indeed, at first this may seem impossible. Diligent practice, however, will permit the experienced swimmer to sustain a serious laceration without bleeding and without even exhibiting any loss of composure. This hemostatic reflect can, in part, be conditioned, but there may be constitutional aspects as well. Those who cannot learn to control their bleeding should not attempt to swim with sharks, for the peril is too great. \nThe control of bleeding has a positive protective element for the swimmer. The shark will be confused as to whether or not his attack has injured you and confusion is to the swimmer's advantage. On the other hand, the shark may know he has injured you and be puzzled as to why you do not bleed or show distress. This also has a profound effect on sharks. They begin to question their own potency or, alternatively, believe the swimmer to have supernatural powers.\n\nCounter any aggression promptly. Sharks rarely attack a swimmer without warning. Usually there is some tentative, exploratory aggressive action. It is important that the swimmer recognize that this behavior is a prelude to an attack and takes prompt and vigorous remedial action. The appropriate countermove is a sharp blow to the nose. Almost invariably this will prevent
142278
The immune system is the system of specialized cells and organs that protect an organism from outside biological influences. (Though in a broad sense, almost every organ has a protective function - for example, the tight seal of the skin or the acidic environment of the stomach.) When the immune system is functioning properly, it protects the body against bacteria and viral infections, destroying cancer cells and foreign substances. If the immune system weakens, its ability to defend the body also weakens, allowing pathogens, including viruses that cause common colds and flu, to grow and flourish in the body. The immune system also performs surveillance of tumor cells, and immune suppression has been reported to increase the risk of certain types of cancer.
24991
The great white shark and saltwater crocodile have gone longer than any other predator on the planet without evolving.  That means they are the best there is at what they do.  As for poision, some types of sea snakes have venom up to 10 times as strong as rattlesnake venom, but they are usually quite docile.
728759
There is a limit to proof.  The family of sharks.  There are\n    hammerhead sharks that have this distinction due to being\n   an excessively large and stupid pod.  A pod reported in the \n   Congo islands mid atlantic is said to eat full size elephant\n   seal and shed their eyeballs quite often.  Many white shark\n   species are truly dangerous and reach 30 feet long.  This is\n   the actual reported animal of most dangerous being it is  \n    tested by sonar as having the lowest IQ and the largest menu.
1183313
Well Boxergirl, I've been scuba diving for 28 years, and just as the surfer said, the best way to defend against a shark attack is to be aware of the shark to begin with! We did a live study on shark attack methods, and the results were very interesting. Almost all sharks will circle their targeted prey several times before attacking. They attack from below, getting an angle from below so that they give no warning. In the surf, and at the mouths of rivers and such, they come from the side, due to no visibility and most attacks on humans there are mistaken identity, because they don't actually see you at all. They bump into soft flesh, and bite in reflex, normally letting go as soon as they taste the blood. Our blood is not the same as marine life, so it's not something they actually like very much. But it can get them excited, so don't take it for granted that they won't attack twice. \n    In the event that you ARE attacked, stay calm, first and foremost! You will have a bad cut, or worse, so you do NOT want to get your heart to racing! If at all possible, locate the shark, and keep an eye on it, while you work at stopping or at least slowing the blood flow. Swimming calmly, not splashing or acting erratic, make your way towards shore, yelling loudly to let nearby swimmers know that you've been attacked. In the event that the shark returns, or makes another pass, you can use both hands and feet to kick and strike in the nose and eye regions. If you have a board, shove the nose of the board at the shark's eye region. Keep in mind that if you are bitten, other sharks may be attracted, so you are in a fight for survival, and there are no rules. You fight to win, no questions asked. \n    Like I said, I've been diving for 28 years, and even with all the sharks dives I've done (435), I've never been bitten. I HAVE had to ward several off when they got too nosey, but no bites. Good luck!!
212592
You are more likely to die in a car wreck than get eaten by a shark.  I want you to read the reference i attached.  If you think about it.  The are more people die in a peanut allergic than shark bites.
629446
Reef Sharks, Tiger Sharks, Nurse Sharks, Bull Sharks, Great White Sharks, just to name a few.
257089
Depending on the fish there could be different obstacles. Certain sharks must continually swim to pass water over there gills to not suffocate. Also in certain shallow water mangroves oxygen depleted water can be another obtacle (except for the lemon shark which can survive better in low oxygen water). I also believe polluted water, such as oil spills and the like, can be perhaps the biggest obstacle of all the fish will face in the respiration process especially around coastal areas.
956438
Either a slick shark or a dolphin. Sharks are amazing creatures which live for hundreds of years and dolphins are just awesome
441775
Snakes often, but not always, have immunity to venom from the same species-they seem to develop this very early from interactions with sibling snakes, though that isnt completely clear.  It would depend on the kind of snake.
277528
A mammal? Nah. An organism? Yep. All living things are organisms, it's just some are a tad more complex than others. If a shark was a mammal, then it would have to have shark boobies, right? Whoa - there's a scary picture... a shark with boobies. Kinda reminds me of my ex-wife....
345043
I don't think it's really possible to know that without testing it. But I would guess that your idea is right, because there would not be enough venom to kill an animal that large. It would probably make it sick. But then again, a whale, or any other really large animal, would react differently to the venom. It might kill it despite the size.
273931
Sharks do NOT die if they stop moving. In fact, many sharks commonly spend time on the bottom of the ocean, engaged in sleep or a sleep-like behavior. \nStrangely, what you cite as a "fact" (which it is not) is still taught in schools, and the reason commonly invoked is that the flow of water through the gills would stop if the animal was not swimming. Actually, sharks are able to pump respiratory water through the gills using movements of the mouth floor.\nWhat _does_ happen when they stop swimming is that they sink close to the bottom. Sharks do not have a swim bladder as bony fish do, and although their enormous oil-filled liver gives them some buoyancy, it's not enough to keep them in midwater.\nPhotographs of sleeping sharks:\nhttp://www.jamaicajim.com/Hshark.jpg\nhttp://world-discoverer.com/photo/burma2003/450-330.jpg
342258
Sometimes Great White sharks will be captured and put in captivity for a short period of time. That would be a good time to jump into their aquarium.\n\nSeal Island is a small land mass located about 5.7 km off the northern beaches of False Bay, near Cape Town, in South Africa. The island is occupied by Cape Fur Seals and a few sea birds.\n\nThe dense population of fur seals at certain times of the year attracts the seal's main foe, the Great White Shark. Seal Island provides unique opportunities for those who wish to observe attacks by White Sharks on Cape Fur Seals and to observe social interactions amongst both species.\n\nAs for this free matter, it depends on where you are located and what mode of transportation you have. If you give more information, it would be easier to help you. This information would enable us to suggest the closest place for you.
219522
The answer is a combination of several factors.\n\nThe skin is designed so as to limit "wrinkling" while swimming. (hydrodynamics) If u look at the skin closely, they consist of placoid scales which r smooth in one direction (swimming direction), and rough in the other direction.\n\nSharks r seriously buffed up, which aids in generating work.\n\nFins stabilise the body to prevent it from swimming upside down or in a circle\n\nThey belong to the chondrichthyes... cartilaginous fishes. This skeletal system is lighter than boney frames and allows for greater flexibility. Both characteristics COULD help in swimming. (There r, however, many fast marine animals with boney frames such as the dolphin or swordfish).\n\nThe tail is the main propulsion force. Which works in coordination with it's respiratory and circulatory system. As water passes over the gills, the lamellae r oxygenated, and at the same time release waste products (co2). So, if the shark swims slowly, the respiration rate decreases... and if he doesn't swim at all, he suffocates. I guess sharks swim fast because they have to. Haha. I hope that's helpful.