How much money would I make if it was off shore welding?

Will depend on time on the job, what ratings you hold, the company you work for, how deep you will be diving, number of actual dive hours compared to on call hours. And of course the total hours a day, and if you are working 7 days a week.

We have discussed this many times on this board, there is a search area to the top of the question board, do a search and you will find tons of great links and answer

But your earnings will be 30 to 70 thousand, with a few making in 100,00