The quick answer is no, but it's a bit more complicated than that.
When a ship is sinking, the crew has to abandon ship. They have to get into lifeboats and go to a safe place. But sometimes the lifeboats aren't enough and people have to jump overboard.
Jumping overboard is called casting off and it's only done as a last resort. The reason is that it's very dangerous. People can easily get hurt or even die if they're not careful.
So, if there are enough lifeboats and everyone can get to one safely, no one will be cast off. But if the situation is desperate, people may have to jump overboard.