I spent two weeks last year looking on and off for a leak. I had ants chew a series of small pin holes in the cove. I purchased a good pair of gogles and filled an old pair of shorts with rocks to make it easier to stay on the bottom. I use plain Kool Aid powder the kind you add suger to and mixed it really strong into a little squeeze bottle. Persistance pays off when you see any thing that looks strange just squirt and if it gets sucked out.

Good Luck,
jen