what is the craziest / funniest thing you have done underwater?

One thing that comes to mind (of many, I must confess) is diving off of Catalina Island with my buddy Pat.
Catalina, for you out of area folk, is located off of Southern California.
It is known for cold water and amazing visibility of fish, kelp forests, wrecks, etc. The island drops off at a steep angle; mostly you dive the sides of the island, unless something is out on the sand.
We were exploring in 80 feet, with maybe 60 feet of visibility when I saw a 30" horned shark. This little bottom feeder is harmless, unless you are a shrimp or something; anyway he got good and mad when I picked him up and held onto him with 2 hands.
Pat came up to investigate, and noticed "Sharky" wiggling around to bite me with his nubby little teeth.
Pat then had the bright idea to pull his glove halfway off and offered the fingertips to the ferocious little guy.
Sharky chomped down, Pat pulled his hand out of the glove and began to laugh...

Which was nothing compared to my laughter as I let go of Sharky, and he quickly swam away with Pats glove...

Well, I haven't done anything that bad or crazy - and is probably tame compared to that.
But, the other week when I went diving, i got whacked (not too bad) by the DMs fins, as he was in front of me, he lowered his head, so he was looking at me between his legs to give me the OK sign to check that I was okay...now that made me laugh :D

Oh, and another thing - when I was doing my OW, I did all shore dives. Now as you come through the gentle surf, there's a bit of a step up in the sand (don't know what the correct term would be), but each and every time I tried to step up, i kept falling over and getting stuck. The OWSI helped me up the first couple of time, but after that he didn't. Some of the other DMs just laughed...As yet, I still haven't done that without going AOT.

A friend of mine told me this story. He has friends that run a dive shop in Cayman and they were there visiting during the off season. Towards the end of the dive along some of the shallower walls the DM motioned my friends wife over. He had a turtle in his hands. and when she would reach in he would pull it a way. (They were in about 20' of water at this point) At the third try to get to it he acted like he was mashing it in his hands. The looks on her face was priceless. Then he showed her that it was a rubber toy. The boat ride back was rather quite.

The DM told them that during the season it gets rather routine and as he knew them he could get away with a little fun... I have been looking for an opportunity to do this to someone ever since...

When we dove for fun off Oahu, we sometimes came across different kinds of puffer fish; green ones, or spiny's etc. They don't swim worth a darn, so we'd run 'em down, catch 'em and shake 'em by the tail. (It's a reoccurring theme!)

When they went to gulp water and expand, we'd help 'em out by buddy breathing and floating them to the surface!

They'd burp at the surface and shrink back down and wiggle away....