Night dives are a blast, especially under a full moon. This gives you some stealth around coral heads. Photo flashes pick up extra color and it's not as dark as one might think.

Hiking at night is also a lot of fun. Not much out there that can hurt you and I never hike with a light on. I sometimes do rounds in my nature preserve at night. Funny story though, another hiker was coming at me from the opposite way, stopped when I stopped, waved when I waved, and turned out to be my shadow backlit from a a streetlight that peeked through the trees. Gave me a bit of a scare but funny later.