Lake Mead ought to be a great place. First of all, start locating, right now, those areas that have a high concentration of people using the water. They are the ones who seed the lake. You can use Google Earth and do the entire shoreline of the lake and look for marked swim beaches. You can usually see the floats that define the area. You will find lots of swim beaches you probably didn't know that existed.
The other choice is an OLD swimming area or a resort area that was built in the early 1900s and the historical society might mention in some of it's books or a curator might steer you to. Some places you'll probably need to rent a boat to get to. Others you can drive to. With the major water level changes in that lake in the last several years, knowing where the shoreline was and what it is presently needs to also be calculated.
In the State of Washington and in the fresh water lakes around here, I have found one thing to be a solid bet. MOST of the stuff will be in water no deeper than waist deep. That where most of the people spend most of their time. I have often thought people wade into the water deep enough to relieve the 'pressure' and that's about waist deep. It's natural for folks to move their arms and hands in the water while wading and after tanning and applying oils, plus the contraction of the flesh from the cold and the water's lubrication, jewelry slips off. Often the break between where people no longer wade and 'push off' and start swimming their first few strokes is where the rings come off as the do the swimming strokes. That area is probably a bit deeper than you can wade...unless you hit the lake at a lower water time.
The exception to the depth thing is a swim/dive platform anchored in deep water. Under that is a good place also as the impact of the body on the water often tears off nice gold chains.
Now the rules:
1. Wear an inflatable life jacket when doing the beaches with a surf. You'll never know when a sneaker will get you. It may save your life.
2. Get a good scoop. There's been tons of discussion here about them. Read about those using a search and choose. Ain't much functional difference between any of the top of the line models. A main consideration is durability. If you drag the thing through the water, the weight is not a considerable issue to me, but it is to others. The lakes around here are usually lots of rocks. I need a stainless to penetrate that hard stuff. When I happen to find a sand beach the digging is actually fun and much faster.
3. Except in the active ocean surf, fill in the holes you dig. The surf is going to fill in the hole faster than you'd like anyway. Sometimes the hole I dig in a lake is a good 12" deep and that's a nasty step off for someone who isn't looking out for that. Could even put a tot over his head which might be deadly. People who leave holes are risking the right to continue detecting there for the rest of us. There's a fair amount of debate about the ocean hunters about the holes but it doesn't take much to kick the sand back into the hole. You'll have to choose what's best in your opinion on that.
4. Don't go in the middle of the swim day when the place is packed. You will get bothered with a ton of unwanted questions and you will interfere with the swimming activity and might risk ejection by the life guards and maybe even told to not come back. Do it early in the morning or late in the evening. In freshwater I'd even use a head lamp and do it at night.
5. Sooner or later you will be asked to help find somebody's keys or a piece of jewelry. This will be a personal decision, but I have always tried to help. No service fee either. That's also a debatable issue. For me, it's just feels good to do something that a lot of others can't do and to make somebody else have a much better day. Sometimes, and this is not the motivation for me, people will tell you about other good areas to hunt and invite you indirectly to better places. That's a reward you can't negotiate.
There's two kinds of waders. Some are really light and are breathable. That's fine for summer. In the ocean's around here, and in the lakes during the winter, neoprene waders are a must. I prefer the waders that have a sock on the end, and then I can put any shoes I want over the top of the bootie. Old tenny runners or...you can get the felt sole shoes that are made for wading slippery rocks in streams and not slip as much as you would with a plain rubber sole.
There's probably lots of other things to consider...but this is a start.
Clive James Clynick has three books out that I own. They all have good learning points in them and even though they sound detector specific that's not the entire content of the book(s):
Pulsepower: Finding Gold at the Shore with a Pulse Induction Metal Detector.
Finding Gold, Silve Coind with the Minelab Sovereign and Excalibur metal detectors.
Advanced Methods for Finding Gold in the Water with the Minelab Excalibur
Do check the "designated" swim areas but I have had much more success in "unmarked" swim areas- watch where the people go! Don't forget to take the trash you find with you. Show those nails, pull tabs, bottle caps, (toxic) lead weights, batteries, pull tabs, shards of glass, etc. to lifeguards and park rangers and you might always be welcomed back for keeping the water safe and healthy. HH!.
