Stellan's Newest Pool Trick

Stellan has an awesome new trick at the pool. OK, I'm being really sarcastic when I say awesome. Honestly, I'm past anxious and moving closer to panicky about the situation. You see, he has no fear of the pool; in fact, I'm pretty sure he thinks he can breathe under water. While I was at Girls Camp, he decided that when he arrives at the pool, he doesn't need to wait for anyone else, he can just climb right in. If you look closely at this photo, you'll see that Kevin isn't even holding Stellan, just bracing to catch him.
He also likes to climb down from the steps of the pool as deep as he can go, and then a step deeper. He really doesn't seem bothered by the fact that his head is under the water and he can't get it out by himself. I am torn between (a) letting him figure it out the hard way just once so he won't do it anymore or (b) pulling him out as quickly as possible before he hurts himself or gets scared. I'm too much of a softie to go with the first option, though.
If that's not scary enough, how's this: last night he crawled to the edge of the pool, turned around to back into the pool, lowered himself in and then held on with one arm. Yes, he was hanging on to the pool wall! He grabbed the side with his other arm and tried to lift himself out again. I had a hard time not laughing at how funny it is to watch a baby try to do something grown up, but I'm terrified he's going to try his tricks when we're not looking.
Oh well, at least he's not afraid of the water.