For $800 you can get some very deep machines that will also work in the saltwater. I just went through this, and didn't even consider the AT Pro, simply because of what you've seen in the above posts; yes it will work in wet / no it won't.
The machines I narrowed my search down to were the Sovereign GT, Explorer SE, Safari, e-Trac, and CTX. The CTX is too pricey for me to justify, so that was out. The e-Trac was more reasonably priced, but for me, again, justification wasn't there, considering the (almost ) same technology as the Explorer and Safari. I really wanted a Sov GT, but analog machines are becoming a thing of the past, and as I'm still new, I decided an LCD would be best for down the road (won't have to learn as much again).
I ended up getting an Explorer SE with the Pro coil. Everything I read/watch gives it a very positive thumbs up in the wet sand & water, as well as very good depth.
If I was more of a land hunter, and looking for relics, I may have gone with the GT, as from what I've read, it gets crazy depth.
So, there are a ton of choices out there that will do better in the wet then the AT, it's just that you need to decide if brand new is a must have requirement for you.