Gold metal detectors?

Very new to prospecting.
I I have 4 questions today
a- Are there metal detectors that are made specifically to prospect gold only?
b- which is the best if they exist?
c- Can they locate gold at a very deep depth?
d- Can they be used on land and in water?

Look forward to receiving your replies.
Thanks

Hi Goldfemme thanks for questions.
A-There are detectors made specifically for Gold,you can find plenty of info here in the search.
B-All manufacturers have gold detectors and the most successful would have to be Minelab.Garret and Whites also have done well in this field.
C-The recent PI detectors have the capability to find gold at excellent depths of 1-2 meters on very large finds.There are some newer units using Radar and other technologies that are able to penetrate deeper.
D-There are gold detectors that are fully waterproof such as the Minelab SDC2300,Garret Infinium.

G'day Goldfemme. Welcome to the forum

a) There are detectors specifically designed for gold nugget hunting, but not specifically for hunting down gold only.
b) A question asked by many. The answer to this would depend more on what type/size gold are you trying to locate, at what depths & in what type of soil conditions?
One of the best hand held metal detectors today, specifically designed for a large variety of shape/size/type natural in-ground gold nuggets, would have to be the Minelab GPZ 7000
c)  That all depends on the in-ground minerals present together with the type/size gold you are after eg; the larger the gold, the greater the target detection depth will be. Specific figures of or on depth, can vary considerably on the type of soil/ground minerals/mineralization present. The greater the in ground mineralization, the less your depth will be on or over a gold target.
d) The GPZ 7000 detector coil, is water proof/submersible to about 3 feet in depth, but the GPZ control box is only weather proof, meaning it can be used out on rainy days, but is not submersible. Other detectors such that of the Minelab SDC 2300 or Garret Infinium L/S (Land & Sea)  are fully submersible to within a certain depth range.  
All 3 above mentioned detectors, are designed specifically for the detection of gold, but will also pick up other conductive metallic in ground targets.
Some of the newer overseas units, such that Deutran mentioned above, need careful researching on, to see what type ground they work best on/in before investing allot of money & finding out they struggle over mineralized soil ground conditions.

Cheers Kon.