In deep/er water, you can approach fish slowly and get very close, often within several inches depending on species and their breathing requirements (tuna have to keep moving, barracuda can sit completely still, etc). When it comes to bonefish or permit in water that is less than a foot deep, photos are typically either via a remote camera that is planted on the bottom and triggered remotely, or the photos are made while the fish is still hooked. The bonefish photo I posted above from a few weeks ago was still hooked and I simply held the leader with my left hand while aiming the camera with my right hand. Light fluorocarbon fishing leader material essentially disappears underwater so it doesn't vividly show up in most photos. Fish will naturally point into current so you just let them 'tread water' in the current and snap away.