A third of the sharks in the world's oceans may become extinct as they're caught accidentally by fishing boats.
That's what an organisation that keeps an eye on endangered animals has said in a shark study.
Sharks are often caught by boats that are fishing for tuna and swordfish. Some sharks are also caught on purpose too, as their fins are used in soup.
Two types of hammerhead sharks have now been listed as endangered, and many others are seriously at risk too.
The International Union for Conservation of Nature is behind the study, and a spokeswoman for the IUCN said: "Despite mounting threats, sharks remain virtually unprotected on the high seas."
Sharks take a long time to grow to full size, and don't have many children during their lives.
The IUCN is also angry about a type of shark fishing called finning, which is when a shark is caught, has all its fins cut off and is then thrown back into the water, often still alive.
Sharks need their fins to swim, so without them are unable to survive.
Shark fins are very valuable as food in some parts of the world, but the meat from the sharks' bodies isn't, so they aren't needed by the fishing boats.
Finning is banned by the European Union, but still goes in many parts of the world.