In my opinion, target separation is always more important than target depth when searching for jewelry at tourist beaches, the opposite applies to searching for older stuff at less trashy beach sites.
It still surprises me just how much value is put into target depth at tourist beaches by people searching for jewelry.
From experience I can tell you the hardest jewelry to detect is often the shallowest jewelry, I know because I make a living snagging shallow gold at heavily hunted beaches.
Gold left behind by speedy grid coverers and golf swingers, gold just waiting to be detected by a person not bogged down digging deep pennies.
I use search coils designed for target separation and my ears as my main discrimination tool.
I also never worry about what Im missing by hunting all the time in all metal or swinging a pizza box size search coil, I concentrate on detecting shallow or partially masked gold.
A gold slump always has more to do with site selection, equipment choice and search techniques than beach or water hunting conditions.
For example, I often use an eight (7 1/4) inch search coil on my Minelab Excalibur to spice things up.
It is a discontinued size search coil, I assume because first time Excalibur buyers always preferred the larger 10-inch search coil model for ground coverage and target depth.
Swing an 8-inch search coil at a trashy beach entrance and you will hear gold the 10-inch search coil will not be able to detect.
A perfect example of recovery speed between targets being more important than target depth.
You can detect a piece of shallow gold, or keep walking looking for a deeper piece of gold.
If you search heavily hunted beaches, why on earth would you be concerned about deep targets.
Fresh dropped shallow gold being hidden because its laying next to a bottle cap or penny should be the thing you are searching for.
Just my opinion, but I believe there is always something to find if you find a way to find it.