The Excaliber is one of the very best for salt water, especially if there is a lot of iron. The Excal will null on any iron targets, unless they are huge, it will tell you when there is a gold ring sitting next to a scrap piece of iron.
Some complain about the different tones it makes for different metals (targets), but for me that was never a problem at all. If your hunting water you don't want to disc out poptops or aluminum, if you do your going to be missing gold goodies also. On gold you want to listen for that nice sharp low growl that gold makes with the excal. Once you hear it you will know what it is.
I have never heard an owner of an Excal complain about the sounds it makes, and when I go hunting the majority of detectors I see in the water at the beaches are Excals. There is nothing I like more then to see someone enter the water near me using a different type of detector.
I have an Excal 1000 and I still love the Excal for water hunting, it is now my backup detector for water hunting only because I lucked out and found a Sov GT for sale that had been water proofed and I snatched it up.
If you don't want or can't afford the Excal, the Whites Beach Hunter ID is a good unit also, but I would not tkae it very deep.
Good luck and good hunting.................