One of the coolest dives I have ever done (and I have done it twice now) is known as a black water Pelagic dive. Basically you leave after dark on a boat and head directly out into the ocean, a few miles off shore. You want to be in water that is essentially bottomless (obviously it isn’t, but it’s over a mile deep).
50 foot lines are tied to the boat and each diver is attached to a line (given the diver the ability to focus on the dive and not worry about how deep they go – all the cool stuff is usually in the 20′-50′ depth range anyway).
At night, things that live at the bottom of the ocean come up to feed and more often than not what you see looks a lot like the creatures from the movie “The Abyss.” I am convinced that James Cameron must have done a dive like this in order to get the idea for them.
The video at the top of this post is of a cone jelly that I happened to see, if you have good bandwidth, bump up the resolution of the playback to 720HD.
If you ever get a chance to try a black water dive, jump on it, this is one of the most exciting experiences you will have in the water. Imagine, total blackness, not being able to see anything except the creatures you find when they are right up on you, no warning, you just see them. Obviously not for the faint of heart, but more for the adrenaline junkies among you.
If you decided to try it, I recommend doing this with Jack’s Diving Locker in Kona Hawaii.