Mary,
We've been houseboating every other year for 20 years, so we've used quite a few different brands of beer (all domestic) and didn't notice much difference in their flotation value. If we have to choose a beer for the official catamaran sponsor, I would go along with Tad and vote for Coor's Light. As long as it isn't one of the many import beers that taste like skunk urine, it's fine with me.
Jack