Wreck photography is very dependant on two key aspects, underwater visibility and the three dimensional form of your subject. While offshore areas around Scotland and its islands generally have good visibility, areas closer to the mainland do tend to be affected by freshwater run off or perhaps pollution from industry and large conurbations. There are also annual plankton blooms that affect all areas, which can reduce visibility over a short period of time (5-10 days). Reduced visibility and light levels will affect the distance you can shot and hence your field of vision, here wide angle lenses and powerful lights or strobes come into play, its always a trade off.