Rick,
I will tell you what little I know, hope it helps.
Are you not finding any targets in the surf, or just no jewelry? Did you try dropping a quarter or ring in the water with a string attached to the ring and see if it sees it.
I originally bought the Corbra Beach Magnet, but returned it the next day because it did not see a lot of targets even laying on the ground. I returned it and got the Whites Beach Hunter ID. Cobra would not see any gold chains, necklaces, or small rings I laid on the ground. It did see large mens rings, and coins, but I didn't want to be walking over a nice gold chain or a ladies small gold ring with a huge diamond on it to dig a pop top a foot away. (just my personal opinion, but the cobra is waste of money to me) Kellyco allowed me to trade up, but I still had to pay the restocking fee.
If your going to be water hunting much in the water, I would spring for the Excal, you just can't beat it. If there is any targets there and you put your coil over it your going to know it. If you don't want to spend the money for the Excal then go for the BHID, although for a few hundred more you get the best. I bought my Excal off of Ebay for $800 with extras and it works perfect, added the Fla straight shaft to it as well.
I try to hunt low tides, at least 2-3 hours prior to hour or more after, depending on how tired I am from fighting the surf or walking.
I myself try to get to the back side of the sand bars, there are troughs there and that is where I try to hunt if possible. Lot of times the surf want allow me to stay there, but when it's calm that is where I head. Look where the surfline meets the beach line, I have jewelry there as well, caught in the roll.
Look for holes or cuts in the bottom in the water and search them. They will move, be there one hour and gone couple hours later. Stuff gets caught in them and can't get out and it also allows you to get closer to the hard packed bottom where most sits.
I would recommend you get a harness with a bungee strap it not only supports the rod and weight while hunting, but it allows you to let go while you dig. The best scoop you can afford is highly recommended. The bigger the bite the less times you have to return to try to find the target. Here where I hunt I am fighting the surf, trying to move me and drown me, I don't have time to play games with a small cheap scoop.
I hope that helps a little. I am sure Sandman will post and he can give you more help.