There are a number of things that could cause the ship to turn around, like lack of food and water or problems with the engine.

Israel says it intercepted the 'selfie yacht' peacefully, offering snacks and water; activists claim abduction while tossing phones into the sea

An aid vessel launched by Greta Thunberg and other international activists headed for Gaza was boarded by Israeli forces on Sunday, mere hours after Israeli officials demanded they “turn back,” the coalition announced in a Telegram post.