Here is another good idea which everyone would enjoy

Imagine being hunted by genetically enhanched sharks and all you do is explore the facility and figure what you have to do and some areas are more scarier than other areas and the longer you wait the faster the sharks break doors and try to get in to where you are.

One area that is the hardest is actually going through an underwater caged corridor where the only thing between you and the sharks in a net of metal wires that the sharks can easily break and makes you want to get out of there.