Hi Maggie. I think cork is risky because it's sensitive to moisture. You'd have to wipe up water all the time. What do you think about polished concrete floors? They can be beautiful and you can find a pro who can make your floor relatively level. These floors will let the view and light be the focus rather than a material with grout lines, etc. which can detract. Here's a link to someone who did this: http://simplyforflying.com/blog/2014/02/afloat-berlin-houseboat/

Good point, Becky. I have spent a lot of time at a retreat center in MA that has glue down cork and even though it's more moisture resistant, we still have to be careful. I would be nervous about having it on a houseboat but it would definitely be a quiet option.