There are plenty of non-macro subjects that are either stationary, or slow enough and willing to let you approach to your desired distance. Wrecks, corals, gorgonians, morays, pufferfish, lionfish, stonefish, scorpionfish, turtles, octopuses, cuttlefish, lobsters, crabs, bottom-dwelling rays, batfish (sometimes), groupers, large schools of fish in general, etc. Yes, some subjects such as sharks and dolphins are fast-moving and generally won't come closer than a few meters - but at these ranges, shooting through that much water, minute differences in image quality between lenses amount to very little, as water degrades the image quality anyway, and sides and corners, where most lenses suffer most, end up being mostly empty water anyway. If wide-angle photography was limited to sea fans, why are people buying all those huge expensive domes and $4k WACPs?