I have found sunken city but have not found enough crab shells to get them made into underwater breathers. I am sick of spending time sailing around looking for giant crabs. Suggestions please!!

If you're running the game unpatched, have a look at page 4 of the Best Tips thread. I recall there was a trick for getting breathers and masks without bringing in the shells.
I never had any trouble getting lots of shells, as I had a char with the Scout skill. She'd announce the arrival of crabs straightaway. And I loved the XP the crabs give.

Traute

You can go through the Sunken City without the breathers if your Athletics skill is high (say, 10) for all your guys and if you have the Breath Air and Restore Health spells (and if you have enough spell points in the Vine and Spirit schools). The Sunken City contains enough "air pockets" where you can emerge from the water.
Otherwise, I recommend searching the crabs. They should be all around. Swim (do not use the ship) to and fro around the shore.