Saltwater beaches require multi-frequency machines. For waterproof your options are the Excalibur, CZ21, Beach Hunter ID, or a waterproof PI. If you can live without it being waterproof you have a lot more options, including all Minelab BBS/FBS machines, any Fisher CZ series machine, or Whites DFX/V3i/Vx3.
The 2 most popular machines are the Minelab Sovereign and the Minelab Excalibur, older Sovereigns can be found in the $400 range.
To answer your question, no a bounty hunter won't work at saltwater beaches on the wet sand or in the water, but will be fine in the dry sand.