More photos of the narco-sub and the “shipyard” where it was built here.
This article has a bit more information but the most interesting part is an almost 30 minute video (in Spanish with English subtitles) about development of semi-submersibles and towed submersible cargo containers. It includes comments by both the Captain commanding the Colombian Coast Guard in the Pacific and a “retired” drug smuggler. Be aware there are commercials, but I recommend it highly. (Ex-WMEC-628 Durable, transferred in 2003, is visible in many of the scenes from the Colombian base.)