GoingWalkabout

Thank you for expanding my vocabulary. Codswollop ...I love it.
The rest of that post was Spot On too.

Thanks for your informed and intelligent comments on the CO2 issue...!

The grating on the entryway is a good idea, as are alarms, a big dog, etc. Same common sense as you use on land for security.
Be wary of using a land based alarm system - sometimes the cheaper systems will not last in a salt air environment, leading to either false alerts, malfunctions, etc.
Good luck in finding a perfect solution for your situation.
Don Weiss
floridayachtsecurity.com