Burkey and LifeStraw are filters, but not stills. They'll make dirty freshwater drinkable. But they won't turn salt water
to fresh, which is what most sailors need.
There are many variations of solar still that sailors can use. I think a small inflatable
one kept Steve Callahan alive on his raft for 76 days or whatever it was. . . .
I'm always curious to see what portable/collapsible/compact versions people come up with, as a cheap
alternative to RO watermakers.