Animal or marine life as a side character that drives the plot?

I’m wondering if there are books similar to what I’m looking for. I’m not looking for anything like Watership Down or Redwall with animals who have human characteristics and wear clothes.

Think something like Free Willy but as a fiction book, or like Remarkably Bright Creatures (which unfortunately I almost liked but didn’t because of a few things). It would be nice if there was more of an ocean setting to the book. Or also, if the main character is studying wildlife (still fiction though), and extra points if character studies marine life.

I’m not really looking for something where the animal that is part of the plot is a dog since this is very easy to find.