Sorry, this opening does not grip me.
The minute an author begins a laundry list of a potential love interest's physical attributes, I think "amateur sexual wish fulfillment". It breaks my immersion.
I do not describe any physical characteristics of my characters that are not required for the plot. If I need Anton to be particularly tall for the plot to succeed, I will have a scene in which Anton's height makes a difference; Anton can get a basketball out of a tree by reaching up and knocking it loose, when nobody else can.
If Betty needs to be particularly beautiful for the plot to succeed, I tend to describe people's reactions to Betty, strangers and others, as a particularly beautiful girl.
If I need a character to be blonde to stand out for some reason amongst non-blonde characters, fine. I'll mention they are the only blonde in their school or whatever. I have used identical eye color to hint at a hidden familial relationship.
You are engaging in "Telling", instead of "Showing". You are giving readers a list of attributes they are supposed to memorize, and they won't memorize them, that is not how this works. Readers remember scenes that carry emotional weight.
To be specific:
Of all the people who wanted to join the trip, Paola was the the last I expected would come.
Duplicated "the".
It surprised me. We barely knew each other at school, and I was pretty sure she wasn't interested in me.
Non sequitur. It doesn't track. Why should her romantic interest in you have any weight in her interest in the trip? Can't she be interested in the objective of the trip? You haven't said you were leading the trip, but even if you were, unless the trip is all about you in some sense, why would she need to be "interested" in you to join the outing?
I didn't pride myself on being a ladies' man.
It isn't clear to me if you are, or are not, a ladies' man.
But if all my rejections had taught me anything, it was this: if a girl never looks at you, it probably means "not a chance."
Rather than giving some flip romantic advice, it might be better to just say you tried and failed with Paola, her rejection hurt, and she'd barely glanced at you since. That's an emotional detail readers would remember.
I would write something like this, off the top of my head.
When I joined this trip, I was surprised to see Paola in the group; I had no idea she had any interest in spotted seals.
Paola was the first girl in school to reject my interest in her. She had barely looked at me since. It still hurt the worst. Nevertheless, I was pleased to see her, to finally be doing something with her other than sitting in class.
The "spotted seals" throwaway helps your setting and justifies your beach reference later. You don't have to be specific about a setting: A trip to someplace frequented by spotted seals is clear. We'll be near the sea, right?
I read the second paragraph as:
"I turned to check on her. She was ambling among the rocks, her back to me, almost a dot in the distance.
Despite that, I could still make out her figure..." [OK, that is red flag implausible. Followed by blah blah {physical attribute inventory} blah blah {poetic sexual fantasy}].
I'm not trying to be mean, I'm pointing out where you lost me. My take:
I turned to check on her. She was ambling among the rocks, alone, her back to me, almost a dot in the distance. Yet even at this distance, I couldn't take my eyes off her. I was mesmerized, wondering what she was looking at. What we would talk about, if I were walking beside her. Wondering if she ever thought of me at all.
Josh, beside me, said, "What's up?"
I tore my gaze away. "Nuthin. Day dreaming."
Josh followed my former gaze. "Oh. I don't think she's with anyone."
I averted my eyes. "Yeah, well. Especially not me."
I resumed our trudge down the beach.
Obviously I expect you to use your own voice, I'm just providing an example. You need to put more emotional hints into your writing. Reader memories are anchored by character emotions.
I'm just guessing at what you are trying to convey, but listing physical attributes of a romantic interest is not a way to convey romantic interest.
Romance is a longing, a desire to be near somebody, wanting to be a part of their life, and not just in their bed.
When authors list physical attributes, they tend to be thinking of their personal preferences. You need to move off of that to something much more common with readers, the emotions we have when we are attracted to somebody, and perhaps even emotions that are not shared by others.
The specifics of what about Paola triggers your hero's unrequited passion for her does not matter. The feeling of unrequited passion for another is something we can all share, male and female, homosexual and heterosexual, regardless of race or language.
That seems to be what you are aiming for. You need to convey what your hero is feeling, not so much what they are seeing and hoping readers will just "get" what he is feeling.