A shark found lying on the floor, especially in a tank or on the seabed, is typically in severe distress and often near death [1, 2].
It might be sleep if … animals have closed eyes. A captive nursehound shark has been documented with eyes half-closed during periods of restful behaviour, and draughtsboard sharks were shown to close their eyes during periods of sleep, whereas their eyes were open during periods of rest.
Resting– Most of the fish varieties prefer resting at the tank's bottom. You may also see a fish sleeping peacefully and misunderstand it as being dead. Energetic fish fall under this category and often go to the bottom to rest in between their active and energetic sessions.
Some sharks can rest without swimming by using spiracles to breathe while lying on the ocean bottom. Sharks might sleep while swimming, with parts of their brain less active, in a state like resting. Sharks do not fall into a deep sleep as humans do, but they get rest in other ways.
Easiest tell tale sign is the pectoral (side) fins. Tucked down/in = aggressive. Out to side = chill.
Sharks can detect odors and they do have a strong sense of smell. Taronga zoo in Australia states that,"[…] Sharks may be attracted to one person to the exclusion of others because the person is bleeding, has urinated in the water, or simply because the person emits a stronger body odor or electromagnetic field."
Shark repellent refers to methods or devices designed to keep sharks away from an area, using magnetic fields, electric pulses, or strong smells (like dead shark extract) to disrupt their senses, with Sharkbanz (magnets) and electric deterrents (like RPELA) being popular personal options, while in business, "shark repellent" also means tactics companies use to fend off hostile takeovers, like golden parachutes. Both marine and business applications aim to deter unwanted approaches, though effectiveness varies and is often debated.
Nurse sharks are slow-moving members of the Ginglymostomatidae family. They're bottom-dwellers, commonly known as sleeper sharks, often found sleeping on the sandy bottom of the sea floor.
Instead of swimming away: stand your ground, face the shark, make eye contact, extend your fins out if you can to ask for space, and if you absolutely need to then push firmly down on the top of the shark's head to guide them away from you, making sure to follow through as they swim away.
Some fish swim continuously, others stay in one place. Deviation from that norm usually indicates stress. Common symptoms of stress include: Fish stays near the surface gasping for breath, indicating that it has trouble getting enough oxygen (the concentration of dissolved oxygen is highest near the water's surface).
Got a sick fish?
Gross symptoms of acute ammonia poisoning are that the fish will gasp for breath at the top of the water surface. When this happens the fish's gills will turn red in colour, and they will look like they are bleeding from the gills. The fish will become listless and sit at the bottom of the tank motionless.
Shark studies have even found that touching a shark's snout can cause it to halt mid-motion and not attack.
If a shark charges, fight back
“That happens nine times out of 10.” If that does not work, and a shark tries to bite a swimmer—or even has a limb in its mouth—Naylor says the best course of action is to poke the shark hard in the eyes.
The risk of injury, let alone death, while diving with sharks is incredibly low. In contrast, more common leisure activities such as biking, swimming and boating result in a significant number of injuries and fatalities each year.
The Great White Shark is considered the "#1 deadliest" due to having the most recorded unprovoked attacks and fatalities, followed closely by the Tiger Shark and Bull Shark, which are also highly dangerous due to their presence in coastal areas and opportunistic feeding habits. While Great Whites are powerful apex predators, Bull Sharks are known for their aggression and ability to live in both saltwater and freshwater, making encounters more likely.
American alligators (Alligator mississippiensis) and American crocodiles (Crocodylus acutus) may occasionally prey on nurse sharks in some coastal habitats. Photographic evidence and historical accounts suggest that encounters between species are commonplace in their shared habitats.
It has traditionally been believed that sharks are repelled by the smell of a dead shark. However, modern research has had mixed results. Semiochemicals have shown some efficacy at getting sharks to leave a feeding area for a few minutes.
Orcas don't just stop at hunting whales and some orcas are known to eat sharks – including great whites. Orcas don't mess about when it comes to hunting white sharks.
And so sharks can recognize me through my scent, my hormonal secretions, but also my body movement, my brain waves, my heartbeat in a certain way the energy that I exude when I'm down there with them.
Sharks are generally most active during low-light periods, specifically dawn, dusk, and night, as these times offer them a hunting advantage with reduced visibility, though activity varies by species and location. While many species are crepuscular (active at twilight), some, like reef sharks, hunt all day, and pelagic species roam widely, so it's crucial to understand local conditions, as increased human presence also influences when "attacks" occur.