@zeborah @Jdreben indeed! I missed that implication.
Also, thinking further, UV (and up) becomes irrelevant, as at smaller wavelength it should scatter fast due to all the micro-stuff in the body of the water. On the other hand, scattering doesn't mean it's invisible. There should be plenty UV in the first 10 meters…
Anyway, don't mind me, I'm just thinking aloud :-)