Drug smuggling: Underwater drones seized by Spanish police - [1]https://www.bbc.
co.uk/news/world-europe-62040790

Jim Bell's comment:
I actually thought of this 30+ years ago,  unmanned, underwater smuggling drones
, but I made no attempt to implement this.  At that time, GPS was very new, sola
r cells were weak and relatively ineffective.

I also figured that it could be an interesting hobby, minus the drugs of course.
  Whether this could get through the plastic trash, and 'ghost nets' I don't kno
w.

References

   1. https://www.bbc.co.uk/news/world-europe-62040790