One of my favourite creatures underwater is the Cuttlefish. And I don't think I put one in Deep Diving - oh, gosh, must check now!
Cuttlefish look a bit like squid or octopus but they're a bit boxier, more inquisitive and lots more fun.
The first time I fell in love with cuttlefish was when I was diving with friends on the south coast of NSW (when I lived inland) and this cuttlefish floated out to check us out. They kind of appear like on a wave as they undulate through the water. One of my friends is a dive instructor and all round unflappable - the kind of person you want to dive with! He took out his regulator (the air giver) and pulsed it near the cuttlefish. Seriously, you could see the cuttlefish writhe in pleasure. So he sat there, taking the occasional puff of air and shooting bubbles over this very appreciative cuttlie, who then hugged his forearm with his tentacles (not in a nasty way, but as thanks). It was the most magical thing. And right there, I fell in love with cuttlefish.
I don't have any pictures of them underwater, just this small cuttlefish 'bone' washed up on the beach. But the Australian Museum website has great pictures and a video link (it's an awesome video!). You can check it out here.