Water detecting on a hot day is awesome! I've done this only a few times now with my EQNX. My little hand scoop has so far been useless in the packed lake & river bottoms, so I just use my hands and dirt digger. My techniques are far from perfected, but so far, they usually work. It gets hard to locate the precise spot to dig when you can't see the bottom, but you get the hang of it.
Here's how it goes for me: I don't use headphones because I don't have waterproof, and I found out the Bluetooth signal cuts off when the control head goes under. I, and anyone around me, can hear the detector sounds when it's above water, but it gets muffled, and sometimes goes "loopy" when under water. This is ok, because you can
feel the signals through the detector's handle. You don't always need to see the TID display either. I dig almost any good, repeatable signal. When the coil is submerged to the point of not being clearly visible, you have to estimate your target's location. You get the hang of it. Then, I use my non-detector hand, holding my waterproof carrot pinpointer (which is now turned on) by the tip end, and reach down to the bottom to try to pinpoint and/or grab the target. Sometimes a little finger digging does the trick. I pull up a hopeful handful with the carrot(by the tip end) in the same handful. If it keeps vibrating when I pull it up, I know I have the target in hand. If not, I keep trying. Sometimes I have to use my digger to dig it up first, then resume "pinpoint grabbing". I don't remember now how I even carry my digger, but I did figure out some way.
A belt and sheath would probably be good. Sometimes while going after the target, it's an easy grab. Other times, I set the Eqnx right on the bottom and go to work until I get it. Another tip: if I don't have a clear visual, I use the tip of one foot to mark the spot before-and-between attempts.
I wear swim trunks with cargo pockets, and carry a mesh bag with shoulder strap for the trash. It has a sleeve for the small bits and pieces. The goods go in my cargo pockets. Gold rings go in my small inside pocket. Hey, that actually happened once!
You may want to devise a system for holding the fish hooks you find. I still need to work on that. Tiny splitshot weights too.
If you can scoop sand, it's a whole different ballgame.
Footwear? Depends on the bottom. Barefoot if I can, or old tennis or water shoes if it's rocky.
Another tip: Sunscreen.