The cloud base was recorded as being around 300 feet that night, so a descent to 200 feet to gain sight of the surface was made. The terrain around the coast rises to over 2,000 feet in places, so descending over water presents the safest option, although not without a degree of risk, as you have pointed out.
Had the weather conditions been better, perhaps an approach would have been conducted from 500 feet, or Black Rock lighthouse would have been clearly visible. We almost certainly wouldn't be having this thread discussion.