
Originally Posted by
Ulth
"The exact impact of Light Staff/Iridal Staff or Apollo's Staff/Chatoyant Staff on Charm is unknown, but they are believed to increase Charm rate by 10% and 15% respectively."
Words like unknown and believed make a strong case for charm being light based.
I'm not trying to dispute that CHR is associated with light. And as I pointed out from the bgwiki people don't actually have proof that light staff does anything for charm. For all you know trying to charm on darksday and failing is just confirmation biases.
As for your logic, charm does not equal love. If you are charmed by something you don't actually love it, you just think you love it. Typically this is done by things that are youthful and beautiful, and personally I associate youth and beauty with water. The fountain of youth for example.
As for more logic as to why charm might be water based a lot of the mobs that use charm moves are water monsters like Lamiae, Poroggo, and Orobon.
With items there are two that give resist charm and have elemental resistance on them. One is the Wuji Ring, it gives resist charm and resist light, however it also gives resist dark and resist sleep. By my best guess the resisting light and dark has more to do with resisting sleep. The other item is M. No.17's Locket which gives resist charm and resist water.