We generally don't give warnings of this type in the hostel to our guest, generally when we feel a place doesn't live to the good name of San Andres friendlyness we suggest our guest to "avoid it", but we feel the need that with this is one we should make an exception and make a strong warning about it.
The Blow Hole or Hoyo Soplador located on the south side of the island,is the definition of tourist trap, pushy sales people and horrible infrastructure. People running this place will try to trick visitors into paying for stuff they don't have to pay, then force them to pay by threating with violence.
Don't take our word for it, read the comments on tripadvisor, google and facebook, most people complain about the same thing, but to top things up on May 2019 there have been 2 documented assaults to tourist by the idiots running this place.
This is a shitty, badly run place that shoould be erased from the list of San Andres' things to do.