I noticed that as well texasbluebell.
It makes sense that she would be buried there, close to the beach where they had said they were -- what is it? 500 feet -- 500 yards?
As others have pointed out, there wasn't enough time to plan a boat trip, not to mention the chance that her body might wash up.
These weren't masterminds, they were panicked young guys who were probably still drunk/drugged and couldn't think straight.