I think NS is closest, looks like an unofficial ships crest to me.
Every official diving badge/crest I've seen (including Aussie, NZ and Canouck) that would have a crown on it, have the diving helmet in profile of face forward.
Possibly the 'Deep Saturation Diver' group asociated with HMS Reclaim, MV Seaforth Clansman or HMS Challenger. The Defence Diving School has always been DDS.