I can answer your question. I have traveled with a SpareAir 3cf bottle for years, which I use for two purposes. First is I carry it when scuba diving for emergency situations (never happened yet) and secondly always take it with me when sailing. Not only is it excellent for checking anchor or cutting line from the propeller, it is also great for retrieving items accidentally dropped overboard just out of reach otherwise (perhaps limited to about 30 feet for safety reasons). I have retrieved multiple items from under the boat without the hassle of suiting-up in scuba gear. Simply grab your mask and fins, perhaps a 5 lb weight if handy, hold the SpareAir in one hand so that you can clear ears with the other if necessary. I find it can be used with no hands by having a good grip on the mouth piece. I wouldn't go any deeper than where you would be able to swim to surface by holding your breath, in case you drop it or deplete the air.

The bottle is filled by using the adapter that comes with it. Simply attach to any FULL scuba tank and open the valve. When traveling it is necessary to de-pressurize the unit, unscrew the regulator from the bottle, and pack in your luggage. I wouldn't store in my carry-on, you might hold up the line if some agent does not immediately recognize what it is. Flying with the unit is legal, but it must be de-pressurized and regulator separated. If you are not planning to scuba dive, simply stop by a dive shop near your boat and have them fill it. You can view it at www.spareair.com (new is about $300.00) or ebay has both new and used for sale. No problem with buying used, but be sure the 'hydro' is current, otherwise you will need to ship to SpareAir to have it serviced at about $75.00.

I find it surprising how easily and frequently my crews tend to drop stuff overboard, just out of reach.