Tertiary paraphilias are non-sexual and non-romantic paraphilias. I personally find it a very interesting topic.
Mine are blood, gore, extracted teeth, mold, bones, corpses, abandoned buildings, and probably some more that I’m forgetting. I can’t really explain why my attraction to those things feel paraphilic, but it does. It’s arousing, but not in a sexual way like my other paraphilias are. I do not posess romantic attraction towards anything.
Honestly, I think the hydrophilia was always there, it was just a matter of getting past the phobia. Which was a gradual process that happened over the course of my early adolescence. I think the biggest single step was learning how to swim when I was around 10. Also, the river thing probably didn’t happen, that was just me remembering something weirdly.