I would say that of all Wide angle photography wrecks are the ones that most commonly people would reach for a rectilinear lens over a fisheye due to the distortion on the straight lines as you say, something such as a 16-35 does give you a more true and straight representation of a wreck, especially when shooting inside. However I would personally always chose the fisheye for a reef, it really makes things pop and allows you to get very close and eliminate a lot of the water between you and the subject giving clean and crisp shots. Both are good options, and if you have the choice it's likely just better to own both so you have variety in your portfolio, the rise of water contact optics though has really reduced the number of people using lens such as 16-35