Hand held magnetometers for divers?

[Bubble]

Hi everybody,

I'd like to get some feedback from those of you who know anything of hand held underwater magnetometers (for divers).

Doing some researches on the net, I could find 2 models only:
- DiverMag1 from JW Fisher (http://www.jwfishers.com/)
- Dicovery Quantrosensing (http://www.quantrosensing.com/handheld.htm)

I'd like to know how efficient they are, how to use them etc. I know that some information is available from manufacturer's web site but I'd prefer field experience...

I'm interested in detecting (underwater) 1000kg of iron buried under 4 m of sand. What about underwater PI metal detectors with large coils? Would they be a possibility (which model?).

Thanks for your answers.

Bubble.