"You weren't like any of the other grass people?" That sounds so lonely. "What do you mean? I mean, I wasn't always like a lot of the other sea monsters because I was curious about the surface, but I wasn't really the only one interested in the surface. What made you so different from all the other grass people?"

Of course, it means that he's not totally in the same boat as Fern (even if they're literally in the same boat), but he's still curious about that because it makes him kind of sad to think there's not other grass friends and family that could show up for Fern. The next part, though, he could relate to, and was pretty helpful in it's own way.

"Yeah. I mean, it's nice that I have so many friends here and I wouldn't trade it for anything, but it's not like any of them can just jump into the water and swim like a sea monster or would think a sea cucumber looks delicious or have ever had their bodies suddenly change withou--"

He pauses, thinking about it.

"Well, I guess you could relate to the changing thing."

And talking about it with Fern is making him feel less lonely. It reminds him that they have some things in common, and while their bodies might not be doing the same thing as each other, they still have being unique in this world in common.