Star Born by Andre Norton

The space they now entered must be the core of the building, Raf thought a little dazedly. For there, towering over them was the round bulb of the globe. And about its open hatch were piles of the material which he had last seen in the warehouse on the other continent. The unloading of the alien ship had been hastily interrupted.

Since neither the merman nor Dalgard took cover, Raf judged that they did not fear attack now. But when he turned his attention away from the ship, he found not only the colony scout but most of the sea people gathered about him as if waiting for some action on his part.