They live right across the canal and I get the impression that its
like when I was a kid sneaking into the neighbors tool shed to smoke
cigs, stupid but I didnt turn out to be a criminal whereas if I had
been imprisoned for it I may have turned out bad.

I understand where you are coming from.

But if you can tell that someone has been smoking pot in your boat you
can be dang sure that the marine police and coasties can tell, too. But
you will be the one losing a boat. Even if the Fed's don't take it,
Florida confiscates automobiles every day that are found to have even a
small amount of illegal drugs in them.

At the very least put a note on your boat where they would see it before
entering, telling them not to use you boat (or anyone elses) anymore.
Also write that you have reported the illegal entry and drug use to the
police.

But there still could be residue in your boat. I know of cases where the
CG wiped parts of cabins with sterile cloth and then sealed them up for
testing.

Then I'd be sure to make a formal report and get some sort of report #
for your own records. If the kids take your warning they'll not be
caught. If they don't then they will, and after ignoring a warning,
should be.

Btw, a couple weeks ago I was visiting a friend. His grown son was there
with one of his buddies. That buddy is in the USCG and works in the DC
office. We got to talking and he said that all the money they were
getting for "homeland security" was going into their drug interdiction
efforts. Yeah, some was into "port security" but for the coasties "port
security" is drug interdiction. After all, traffic is traffic. Smuggling
is smuggling, whether it be pot, cocaine, heroin, people, or explosives.