Tudor Marine Nationale Sub

[Cantab]

At the recent Head of the Charles Regatta (world's largest rowing regatta), I was spectating next to a Frenchman who was discussing what he described as a very rare Tudor Sub. He mentioned that the French Navy (Marine Nationale) issued several Tudor references to their divers, commandos, and submarine officers from the late 60s to the late 70s. This sounded intriguing, and I wonder if anyone can elaborate on sources for these watches. While I am sure that they are expensive, it is hard to imagine that they are valued in the the range of the famous Rolex Mil Subs. An issued diver's watch from the 70's is at the top of my list for an aspirational acquisition, but a quick search on TRF and C24 yielded no results. Any thoughts or comments would be greatly appreciated.