Sharks keep them in their body, which keeps them "salty”. Sharks take in small amounts of water through their gills (by osmosis – because they are slightly saltier than the sea) which means they don't directly have to drink. Sharks also have a salt gland (in their rectum) to get rid of any excess salt they may have.
Unlike bony marine fish, sharks don't drink water. The blood and tissues of sharks (and other cartilaginous fish) are extremely salty, containing high concentrations of urea, trimethalamine oxide, and other salts.
Sharks can slosh water around in their mouths to manipulate food to some extent, but swallowing is another matter. They may compensate by using the muscles of their pectoral girdle – the equivalent of our shoulders – that supports and powers the anterior ns during swimming.
Instead, water flows through their gills, which extract oxygen and pass it into the shark's blood. Without water, the shark's gills cannot function, meaning that no oxygen would enter the bloodstream, and the shark would asphyxiated.
Is it possible for a shark to drown? Despite being ocean dwellers, most sharks need oxygen to breathe. They don't have lungs but instead absorb oxygen from the water using their gills. If there's not enough oxygen available in the water, sharks can't breathe and can easily drown.
Whatever method they use to breathe, sharks are able to engage in periods of deep rest while still but do not fall asleep in the traditional sense. Lacking eyelids, their eyes remain perpetually open, and their pupils still monitor the motion of creatures swimming around them.
Different sharks breathe in different ways, and this influences how they rest. Some species are thought to 'sleep swim', others lie stationary on the seafloor, and some snuggle up in groups or someplace out of sight where it's safe to rest such as in a cave or in the sand.
From precipitation to the land to the rivers to the sea
The rain physically erodes the rock and the acids chemically break down the rocks and carries salts and minerals along in a dissolved state as ions. The ions in the runoff are carried to the streams and rivers and then to the ocean.
If you drank seawater, the salt would get absorbed into your blood along with the water . That would make your blood too salty. So, your kidneys would have to remove the salt. But to do that they would need to use even more water!
The answer is: they do not drink water like land animals do, as they don't risk dehydration from the sun. This goes for all the marine mammals like whales, dolphins, seals etc. The way they get water is through their food.
Most fish breathe when water moves across their gills. But if the gills are damaged or water cannot move across them, the fish can suffocate. They don't technically drown, because they don't inhale the water, but they do die from a lack of oxygen.
Unlike their noisy neighbors, sharks have no organs for producing sound. Even their scales are modified to allow them to slip through the water in ghost-like silence. But there are persistent reports from New Zealand of a type of shark that actually barks like a large dog.
Many different species of shark have been documented regurgitating the indigestible parts of whatever they recently ate. Sometimes the stress response is so severe that they vomit up their stomachs. This gastric eversion is triggered by a stress response, but the behavior itself may be a natural occurrence.
Human blood may attract and excite sharks, and divers and swimmers should avoid or come out of the water with bleeding injuries or, for women, when menstruating. Similarly, feces and urine may be attractive, and should not be scattered indiscriminately where one swims or dives.
Sharks have been found to contain the highest concentrations of methyl-mercury than any other seafood due to bioaccumulation and their place at the top of the food chain. Cooking does not eliminate mercury.
If they stop swimming, they stop receiving oxygen. They move or die. Other shark species, such as the reef shark, breathe using a combination of buccal pumping and obligate ram ventilation. When swimming slowly, they can use buccal pumping to supplement the amount of oxygen received from ventilation.
I've seen great white sharks pass up delicious chunks of tuna and appear bored around groups of seals. I don't think they waste energy randomly attacking things if they're not hungry. But sharks are pretty curious creatures and sometimes they'll gently bite things to 'test them out.
Most sharks live 20 to 30 years in the wild, but some species can live far longer. At the extreme end of the longevity scale are Greenland sharks, which can live at least 272 years, making them the longest-lived vertebrates (backboned animals) in existence.