Wet salt beach hunting means one thing...a nasty environment where things can get corroded easily and units need to be rinsed off/wiped off and cared for.
So, it's seems logical a waterproof unit is probably the best bet before any other non-waterproof unit.
That leaves the CZ21 or an older CZ20 as the only Fisher choice. Only caveat with this unit is the coil is hard wired in.
If you can find an older CZ6a, which is the best water/dust resistant unit Fisher made that wasn't waterproof, that would be my next choice.
Any of the other CZ's are next in line.
All CZ's that are up to spec will run equal or better than an E-Trac or Sov depth wise, coil size being the same or comparable for all units.
To tell you the truth, I have an E-Trac and it runs really nice in the wet sand, but one time I was too busy diggin and did not pay attention and it almost got swamped by a wave so that unit doesn't get any where near the water ever again !
Also have a Sov GT and use the 10 inch stock coil and the 15 inch WOT and it runs great. But I still use my CZ6a and CZ20 about 80% of the time in the wet sand. Just too used to it I guess and they always find me good targets.