If you take a look at submarines like this one they blew up

https://truthsocial.com/@realDonaldTrump/posts/1153966324414...

They are almost always used as narco trafficking. However, we only know that is usually the case, not that this particular one was used for that purpose.

There are a handful of civilian legal use submarines of this form and submersibles used for tourist and science purposes, however if a scientist or tourist rich enough to fund recreational submarines were killed it's likely the family would have come forward by now.