There a lot of polite, & or sneaky ways of bringing up the wisdom of getting a cat instead. Particularly when you put the throught into someone's head
so that they think that it's wisdom was arrived at by them. If, in fact, they're insecure enough so that discussing it openly & honestly won't work.
With the primary one (truthfully) being that the risk of motion sickness for those new to sailing, or who are rusty, will be significantly lower on a catamaran
. Which also sync's up with the fact
that if one person is seasick, the risk of others falling prey to mal de mer is pretty high. Given how people react to hearing, seeing, & smelling others who are suffering from it.
Thus chartering a cat for that many people, for a full week, is akin to trip insurance
. And besides, who wants to be sick while on vacation in a gorgeous local with great sailing conditions?
Or, sell it from the fishing
POV. In that you can trail more lines from a cat, & they also sail at speeds that are better for trolling. And who doesn't like fresly caught seafood? So...
Plus they're much easier to cook underway on. Particularly for large crews like you're talking about.
Also, there's the ease of boarding thing. From dinghies, water
toys, or directly from the water
. Ease of loading dive gear
into the dink. Room for water toys onboard....
PS: There's a lot more privacy on a cat as well... Especially for couples