How long do a turtle has to stay in water?

Sea turtles can stay under water for almost their whole life! One of the only times they come out of the water is when they are going to lay there eggs because they lay there eggs on land and leave them and then the babies have to find there way back to sea all by themselves. Most of them get eaten by seagulls on their way so that's why there are not so many sea turtles... Most of them get eaten.