I don’t mean to be picky (which means I am about to be picky) but this guy is not sitting “where fresh and salt water meet.” That boundry, the halocline, is at a shallower depth, usually between 35 and 50 feet deep in these cenotes. The halocline doesn’t present as “murk.” If you manage to approach it without disturbing it, the halocline looks almost like a mirror in the water. Passing through it is like stepping into a Van Gogh painting, everything is sort of swirly.
Either way, this place (Cenote Angelita) is stunning!