On Tue, 14 Jun 2011 09:04:40 -0700 (PDT), Frogwatch
wrote:

Thinking about my wayward dinghy caused me to remember another
wandering object on one of my recent Bahamas trips.
I had finished cooking on the magma grill (spoiled crew demanded warm
mac and cheese) and tried removing the 3/4 full propane canister.
Once removed, it was leaking propane, uh oh. No way this thing is
staying aboard. I cannot leave it on the grill cuz it is choppy and
the grill has to be stowed. After considering various options, I
decided littering was the safest one so I simply threw it overboard
and settled down to do some reading. A bit later, "Thunk, Thunk,
WTF?", I go outside and look down and there's the canister bumping on
the hull so I fished it out with the crab net.
This time, I really heave it far away and go to bed. Yeah, you
guessed right, middle of the night, "Thunk, Thunk", tide had carried
it right back to me.
Realizing I'm gonna have to get serious about this, I pull out the
tide tables and turn on a light eliciting lots of complaints from
sleeping crew but I find the tide will be running out in an hour. So,
I wait up till then and finally get rid of the canister but never did
get back to sleep waiting for the "Thunk, Thunk" again.

Why didn't you just slowly open it up down wind, let it empty, then
tie it up outside overnight?