I am primarily a land hunter due to my geographic location (outreaches of Western Kansas) but I LOVE water hunting when I can. About 3-4 times a year I get to go to a fresh water lake and detect and I most always find some nice bling. I have a few tips that I have picked up. Others may have already commented these. I'll try to post some pics of my homemade gear tomorrow.
1. I would not enter the water without water sock or shoes. I have scooped up treble hooks, needles, shreds of aluminum and on one occasion a broadhead arrow
.
2a. Start shallow so you can watch your spot as you scoop and then gradually work deeper. once you get the hang of it, the scooping gets much easier. Go slow, it's like learning to detect all over IMO.
2b. My best luck is in what I call the "Mommy Zone" which is knee deep to waist deep. Not that I haven't found good stuff other places but this is the higher percentage zone for me.
3. I made a plastic scoop like this
http://www.tcmetaldetectors.com/graphics/wilcox450.jpg with an identical feed scoop that I bought at Tractor Supply for about $2. I attached a metal tent pole to it with u-bolts and bent the pole a little bit to get a good angle. Works awesome for no more than I use it but if I did much more water hunting I would definitely buy a quality stainless scoop.
4. My finds I put into a contraption that I made from half of a minnow trap (like this
https://www.amazon.com/Gees-Gee-Feets-G-40-Minnow-Trap/dp/B0033OI7V4) with a pool noodle zip tied around the top. I have a 10" piece of nylon cord tied to it and a nylon belt and I just pull it along behind me. This works very well for where I am but if you are detecting places where there are a lot of waves you will have to find another place to put finds or they will get dumped out. I use this because that's what I had laying around.
5. It is much easier to scoop if you can let go of the detector. I let my AT Pro go and if floats beside me, tethered to me with the headphone cable, not sure about the CTX.
6. Speaking of headphones, I had my heart set on a pair of waterproof headphones but I'm only comfortable in water up to my shoulders so I never ended up buying a pair. The main reason I never did is that i figured if I accidentally dunk the ones I have, I can get a new pair of garrets for about $25 instead of $150 for GG Amphibians.
7. Like I said, I"m good up to about my shoulders. After that my positive buoyancy makes scooping with any control really difficult.
8. Be ready for an audience. I usually hear people talking about me from the beach and they assume I can't hear them. Kids get really curious. Be ready to not show emotion when you pull a nice shiny ring. Just put it in your finds holder and look at it later.
9. Good luck and I hope you enjoy it as much as I do.
Edit: I forgot to mention. When I pinpoint but can't see my coil, I get the target to the toe of my coil and then put my toe against the heel of the coil. Then I move my detector and put the scoop right on top of my foot and then pull my foot out and use my foot to push the scoop into the sand/mud/gravel. Also, keep a wide stand if you are more than waist deep, it will help you keep your balance.
Another tip that I use, when I get in above my waist I always get to the deep side of the target and push the scoop toward shallow water. That way I know that I won't push it into water that is too deep for me.