Frank wrote:

Don't see why they would not work in lake water, with a pre filter/strainer
of some kind to remove junk, and an ultraviolet sterilizer after the unit to
get rid of bacteria. Salt water would probably be too much.
Frank

If you're relying on UV to sanitize the water, you'd better plan on a
recirculation system that runs continuously - not really desireable in
boating application. UV is a very poor sanitizer, especially in a
one-pass installation.

Keith Hughes