We bring them if we're double-handing in the open-ocean, otherwise not.
Not really needed if you're in a big charter cat filled with people and sailing from bar to bar around Drake Channel.
<img src="http://www.traveltalkonline.com/forums/images/graemlins/drinking.gif" alt="" /> <img src="http://www.traveltalkonline.com/forums/images/graemlins/band.gif" alt="" /> <img src="http://www.traveltalkonline.com/forums/images/graemlins/dine.gif" alt="" />
We've had the CO2 cartridges confiscated at the airport... on the way back thank goodness. Best done in checked baggage.