Sigma 10-20mm f4-5.6

A good choise if you don´t have the money to buy a Nikon lens. Pretty fast and sharp and great for bigger animals like manta rays etc.

This lens is very sharp and the focusing is quick, silent and accurate. The rectilinear design renders square images but at 10mm the corners seem to be stretched out (accurately rendered but so extremely wide they seem distorted). If you like that effect then this lens holds a lot of creative opportunities for you. I personally prefer the distorted look of a fisheye lens as the corners seem to be more contained. Still, a very great lens.

Good, but too heavy for the diving trips !!