The trench

You love the sense of danger the trench gives you.

Normally, any sea explorer will tell you that you have to be mad to go into a trench willingly. At any moment a boulder could fall and crush you. Your luck has always given you fortune, so there's nothing stopping you from soldiering on.

You travel slowly. Your headlights are the only thing stopping you from ramming face first into the trench walls. Not only would break the glass on the view port, but a tremor could easily set free one of those deadly boulders you thought about earlier. In fact, a chill ran down your spine when you saw a stray rock fall in front of your headlights.

At least you thought it was a rock. It moved a little faster than you thought it should and you couldn't find it when you stopped to catch your breath.

You happened upon a small cave. It's too small for the sub and you'll have to use a pressure dive suit (you also designed this yourself) if you want to explore it. You'll be moving slower than if you were in the sub, but at least you might find something of interest.