Well, the PAN political party in Mexico seems to have been busy cleaning
things up. According to the US Department of State for travel in Mexico
"Mexican insurance is required for all vehicles, including rental vehicles."
They don't mention it specifically but there is now a minimum liability limit - called a Civil Liability - of $5000. Like other nations in the world, one could probably post a bond in place of that to be legal
. Live and learn...
The State Dept. doesn't say anything about recreational vessels.
In any event, liability insurance is a really good idea, considering that this covers what damage you or your property does to others (i.e. your fault) and is available over the Internet
for pretty small premiums (on the order of $200 a year). Clean wake, etc. etc.
I am always wary of companies advising that one needs their product even if they are correct - the conflict of interest is just to prominent.