I guess this is something Aquaman can do.
What use would Aquaman be for building a bridge? Get the fish out of the way? Make sure they don’t get attacked by sharks?
I guess he could help do some of the legwork underwater, but he’s just one man. And he’s a man whose own kingdom means a lot more to him than the surface world.
But I guess this is 1970s Aquaman, so he’s much more buddy-buddy with landlubbers.