I’m actually pretty frustrated with the dialogue on this one because, but gonna post it and move on.

↓ Transcript
Selkie: Mister Pohl and Scar should just let others help!

Gien: That’s not really possible. The Echoes are the only ones who can generate the energy necessary to cut and
shape blocks for houses.

Selkie: No, they aren’t. Humans don’t have Echoes, but they still make giant buildings. They just build tools to help them do it better!

Gien: I promise you, we have thought of that. Pohl and Scar can make tools for the rest of us to help with small labor, but not large-scale production.

Selkie: Then why not use human tools? We’re already friends, and Mister Brown loves helping!

Gien: Human construction tools don’t work underwater, child

Selkie: Then don’t build underwater! Build on the surface! One of us! One of us!

Reasons for frustration: underwater construction is a real thing, but it doesn't work for that to be the solution here, and lots of unnecessary fussing was spent explaining why that won't work before I just opted to cut it and skip the issue.