check out www.specialwelds.com and read all about it

In the following link find Chapter 13 it deals with underwater welding
http://www.fortunecity.com/village/lind/247/index_WELD.htm

Sorry, it was chapter 12.

I know that the arc in wet welding is intiated by touch to complete the electrical circuit " when using SMAW process"...However, the welder says that the clearance or the arc lenght is not long or varies in length like in the surface welding. If the arc length is too long, the arc will extinguisg due to the water leakage in this spot...And if the arc is too short though, excessive penetration may result..The welder/diver should be skilled to maintian a stable arc when wet welding..I saw some welders trying the arc first in a tank to adjust the ampere and so..Further readings u can find in the

Welding handbook_ Vol. 2_ Chapter 10 (Underwater welding and cutting).
as well as the websites included here in the thred of course...I went through the fortuncity.com and it is very good...check it out..