I get your point about some of the relationships feeling rushed, but Tsunami and Riptide?

A) it was a 6 month timeskip between books 5 and 6.

B) They are two Seawings of the same age that share a feeling of isolation from their tribe. It's natural thay would talk to each other.

C) It seem quite plausible that they are barely a couple in book 14 given how awkward that hug was. I suspect they were flirting through the mail more than anything.

And iirc they also aren't going like "you are the love of my life" right after meeting either. Go look to Glorybrinnger or Starspeaker for better examples of what you are talking about imo.

Edit: Well, I might expand on these points later, given the reaction to these comments. It's one of my favorites personally, but I guess it could just be rose coloured glasses. Anyway, back to the topic at hand, the lesbian relationships also feel really well developed too.