Speaking of surprising underwater things that weren't actually underwater: During my recent visit to Chile, we saw the
Museo Maratimo National (National Maritime Museum) in Valparasio.
Anyhow, one thing I saw there that surprised me was one of the
Fenix capsules used to rescue 33 miners from a
mine collapse at 700m (2,300ft) depth in 2010, crediting a naval task force with its design and implementation (not highlighted: designed in collaboration with NASA). [Link: wikipedia]
Mine collapse rescue by a
naval task force?!
Oh, right -- Chile has submarines in their fleet, and their navy would have technical experts on engineering and the decompression issues on ascent during the recovery operation.