Re: Metal Detectors for Beginners - Whites 5900 DI & 5900/DI Pro SI
The two Whites you mentioned are fine and not toys, but are certainly dated. They are also not the best for saltwater beaches in the wet sand. Dry sand, OK. The others mentioned are top of the line detectors an well worth the money. However you can do well with less expensive machines from the major manufactures.
If you are planning to get into the water, you'll need a full underwater detector like the Tiger Shark, Beach Hunter II, Fisher 1280, CZ20, or Excalibur 1000. The PI type like the Garrett LS are very deep, but you will dig deep for iron most times.