Sigma 17-70mm f2.8-4.5

All around good lens for underwater. All around meaning pretty good macro, pretty good wide. I have shot nudibranchs and manta rays on the same dive with this lens. The reality is, it is not exceptional at either macro or wide. If you are taking this lens down, you are most likely using a dome port. You cannot get really impressive macro shots using a dome port. If you shoot it wide, it is pretty good. Just not real impressively wide. This lens is perfect if you are about to do a dive where you don't know what you are about to encounter.