If macro and super macro are the best model of shooting, as Sean recommends, you'll want to add an accessory lens on your system. A +10 seal diopter lens from Aquatica will include those small sea critters filling the frame. If you will bring the tiniest of tiny to the big screen, Sean proposes the for incredibly pointed 2: 1 macro images (twice life size) or the alone or with the addition of the Multiplier Lens to discover the headshot of the pygmy seahorse. If you love shooting the big picture, the RX100 III's native 24mm will supply fairly wide coverage of the underwater scenics; however, if you choose up to 168 degrees of ultra-wide shooting, add an iTorch M52 on your system. ergonomics.