This will be the class slogan, not only used for the T shirts.
Right, but it still needs to be INTERESTING and EYECATCHING.
Like Hog's Breath Beer has that slogan, "Hog's Breath is better than no breath at all."
If you have a slogan like, "BEWARE: This cat can be addictive," you can actually have a whole series of "ads" on different shirts based upon that slogan. And they won't really have anything to do with sailing.
Could be a great ad campaign for the boat.