As an underwater photographer, I have to set up my camera, lens, housing, and lighting kit, prior to getting in the water. Once beneath the surface it is not possible to change lenses. Many times that means passing up on subjects as its hard to photograph a 1 inch nudibranch when your kit has a 15 mm wide angle lens. So the day before the dive, I consider conditions, the group I am with, if there is a subject in particular I might find, then decide on macro or wide angle and select the appropriate lens, dome or macro port.
When creating landscape photographs, I know I want to create wide angle environmental style portraits and set my camera up with a 14-30 wide angle lens. Just for safety I might put the 14-24 lens in my bag as a back up. Both are great for creating landscapes and switching would not change my mindset in terms of composition or style.
If planning a dive and there had been a lot of rain I might set up for macro as the visibility might be diminished. My goal would be to try to create portraits of small critters encountered during the dive. Fish are wild and move around and you can never be sure what you’re going to see. Thats why it is so important to be set up, so when the moment arrives, you’re ready. If conditions are good and the visibility is great I might set up with a 15 mm lens, and in this case go hope an eagle ray, manta ray, shark, or turtle swam by.
To sum up lens selection is based on subject matter and conditions for both underwater and landscape photography. While you cant change lenses underwater and can on land, as much as possible I use only one lens in the filed. The less changing of gear in the field the better as sand, salt, particles, and gunk happens.
IF interested in learning more consider a private workshop.