I've used my Tejon on dry sand with great results, but it's useless over wet salt sand.
My Mojave does a lot better on wet salt sand with the 7" stock coil and the High Mineralization setting. It does start to chatter if you put a larger coil on it, though. But the 7" is really stable and has found me some nice targets.
The Simplex does sound like a promising option, but we'll have to wait and see if it continues Nokta/Makro's track record of producing good machines.
Despite Tesoro closing up shop, I admit I'm still really tempted to pick up a Sand Shark for water hunting. It may not be the most rational choice but... Tesoros are like potato chips: it's hard to stop at just one!