I was just going to post the link that HotI shared with you. The article that Kelly wrote has a lot of good info.
Also, it might help for him to think about what exactly worries him about waterbirth. You'll be in the water labouring for a couple hours, most likely, (it helps a LOT, IMO!) but in most cases, as soon as the baby is born, you scoop them up onto your chest, so baby is in the water for only a few seconds. Babies don't breathe under water, and in any case, the baby is still being supplied with oxygen from the placenta. So there's not really any reason to worry about the baby. Fetal monitoring can be done intermittently with a doppler just like with a "land" delivery.
Some midwives are not familiar enough with water birth to assess blood loss in the water, so you might have to get out fairly soon after baby is delivered, just so that they can be sure about how much you're bleeding. That's the only real concern that I can think of for you with a waterbirth. And if the midwife is familiar with waterbirth, that wouldn't be an issue either. But you'll probably be ready to get out fairly soon anyways.

Here's another one of the BB articles that has some good waterbirth info for you.
https://www.bellybelly.com.au/birth/...r-a-waterbirth

Enjoy the planning, and all the best for a wonderful birth!