A thick fog with strange properties surrounds the island, and in certain areas it's so thick you can't even see your own hand. Time passes strangely within it, and sound doesn't travel well. These areas shift and move throughout the island, so you may turn around and suddenly find yourself separated from your group and lost within one. It may seem like only a few minutes to you, but its possible that hours have passed once you catch up with your friends.
THE OOC
Think of this as your IC "out" so if you're gone for a few days you don't have to wrack your brains over why your character wasn't interacting and where they've been until now.
Easy solution: because they were lost in the mysterious fog of the mysterious island. It's very mysterious, and such things are known to happen.
Mysteriously.