Hi all, I've never used dry ice (great opener for an answer to a dry-ice question ;-), but I always assumed it'd be great in a boat icebox. Then, a couple of years ago, in the Pacific NW, I had the opportunity to buy ice at a real ice plant (fish-boat-dock ice plant), instead of the grocery store. They had both dry and regular ice, but advised against dry ice for my application (galley icebox). What they said is (IIRC) that exposure to air makes the dry ice lose effectiveness, so in a typical boat ice box - which you open relatively frequently - it doesn't work as well as regular ice. They said that dry ice is very effective for uses such as a large salmon that you want to send to friends across the country; it's packaged with dry ice, sealed, and not opened up again until it reaches its destination. So I suppose it could be useful if one brought a second cooler along for "later," not opening it until the regular icebox was warm. Probably a bit elaborate for an "M" though. Does anyone have comments? I'd love to hear the reason why this is or isn't true about the dry ice. --- Rachel