Enjoy this video of drugrunners in a semi-submersible vehicle getting collared by the U.S. Coast Guard. How dangerous that thing must be!
U.S. Coast Guard Cutter Munro (WMSL-755) crew members board a self-propelled semi-submersible drug smuggling vessel (SPSS) June 18, 2019, while operating in international waters in the Pacific Ocean. SSPS vessels ride low in the water, half-submerged to evade detection.
Apparently newer models are fully submersible.