What happens to items left in the ocean if the last Presence of Ocean's Hungry Grasp is removed from the Island Board?

Pieces not representing humans physically remain where they are, but are considered out of play until/unless that Ocean returns to play. Invaders and Dahan are cleaned up to the nearest legal land (though it's rare for this to be relevant, since they're also cleaned up to the nearest legal land every time you complete a primary action.)