There are several options...
a mesh ring sling like those Comfy Joey and sleeping baby productions sell
a water wrap like the gypsy mama water wrap ...I think babyette has one too maybe?
a carrier made from solar weave like the solar weave connecta or boba air (that may not be solar weave but can do water and dries quickly) - both of these are buckles.
There used to be some solar weave mei tais out there but you'd have to hunt for a used one.
And it probably goes without saying but no back carries in the water :)