Shoes are off obviously so he doesn't get them wet. Goggles are so he can look for his drill underwater when he falls in. My concern is the debris from drilling will fall in the pool.
Wow, How STUPID, can you get?. Imagine, if you or the drill slipped and you fell into the pool, holding the drill. And I bet that, that drill is not fed via a GFCI either. Some people are probably better off dead.
Reminds me of a close friend I had back in the late 60's. Working on a dock in the water. The guy he was working with gave him an electric drill. Started it and the was the end.