Hi Jeff,

Well there are two kinds of beaches. Salt and fresh water. Salt water beaches have a lot of mineralization and the ideal machine for those are called PI or Pulse Induction. Get a fully waterproof PI machine and you can wade out or even scuba. And they aren't as affected by the minerals. Any machine can do the dry sand successfully but the wet sand and in the water will be the most challenging at a salt water beach.

It's not that you "can't" do wet salty sand with a regular machine if you turn down the sensitivity and try not to touch the coil to the sand. If you do your coil can false, or make a sound when it touches. All detector coils are waterproof but their control boxes aren't all waterproof. 

Currently the Milelab Excalibur II is the most popular beach machine. Whites makes the Surfmaster at half that price. And Garrett has the Seahunter II. And even cheaper, Tesoro makes the Sand Shark. Normally I'd say look into used if you are on a budget, but with waterproof detectors you probably want new with warranty.

If I got to the ocean more than once a year, I'd probably get a Whites. Hope this helps!