For shallow water detecting and diving in fresh and salt water and on the beach (wet and dry) sand VLF multifequency metal detectors are best. The Minelab Excalibur, Fisher CZ21 and Whites BHID 300 are the most popular in the ordered listed.
IF you want maximum depth, dig all - no discrimination, you will want a Pulse Induction (PI) metal detector.
In comparison to multifrequency beach detectors which are more general purpose, PI detectors are more selective.
The most popular PI detectors for shallow water hunting, diving, and wet sand hunting on salt water beaches are the Tesoro Sand Shark, Whites Surfmaster PI Dual Field, Garrett Sea Hunter Mark ll, and the Garrett Infiniium LS (land & Sea).
With the exception of the Garrett Sea Hunter Mark ll and the Garrett Infinium LS all of the coils and headphones on the above multifequency VLF and PI detectors are hardwired.
Many beach hunter prefer the more flexible and powerful Minelab Sovereign (compared to the Excalibur) as it is less expensive and since it is not hardwired t supports different coils, head phones as well as meter and an inline probe accessories. It can be used for dry and wet sand hunting at fresh and salt water hunting and up to knee deep water (with great care - it is not water proof). I do not recommend it as it is not as rugged as the above detectors (drop it in the salt water, and it becomes a very expensive boat anchor), and it is no longer in production, meaning that it cannot be repaired, once parts are used up. It is a shame, as in my opinion it is the best of the best.
All-Terrain VLF and PI detectors can also be used for shallow water salt and fresh water hunting such as the Minelab multifequency CTX 3030 and the new Garrett ATX Extreme PI. As these detectors are more expensive and a depth limitation of only ten feet (whimpy- in my opinion) I do not consider them suitable for diving.
Use of the Garrett AT Pro which began the All Terrain category, is iffy - success depending on your skills and how mineralized the soil is. You may be able to get by with it in lightly mineralized soils, most likely not. Great detector other wise, priced to be affordable, lot to like.
