Sister Planet

In Poul Anderson's "The Big Rain," people from Earth have colonized and hope to terraform the uninhabited desert planet Venus whereas, in the same author's alternative Venus story, "Sister Planet" (Anderson, Dialogue With Darkness, New York, 1985):

"The first explorers had expected desert but instead they had found water." (p. 96)

This is because, in the upper atmosphere:

"...water vapor was frozen out. Thus absorption spectra had not revealed to Earthbound astronomers that this planet was one vast ocean." (ibid.)

As I have said more than once, Anderson gives the impression of systematically examining every possible alternative version of any science fictional idea.

The "Sister Planet" Venus is a landless ocean with floating islands and a humanly poisonous atmosphere whereas CS Lewis' Venus/Perelandra is mostly ocean with floating islands but some Fixed Land and a humanly breathable atmosphere. Burroughs' Venus/Amtor has people living in giant trees and enough seas for his first volume to be called Pirates Of Venus.

The "Sister Planet" "Venusians" are friendly, trading cetoids;
Lewis' Venerians/Perelandrians are green-skinned unFallen dwellers on floating islands;
Burroughs' Amtorians are human enough for the Earthman hero to marry a princess - a necessary prerequisite for any ERBian planet;
Stapledon's Venerians are uncommunicative, hostile, dolphin-like sea-dwellers, exterminated by invading Terrestrials;
Heinlein's Venerians, appearing both in "Logic of Empire" and in his Scribner Juvenile Space Cadet, are cooperative, frog-like swamp-dwellers.

For some reason, Terrestrial sf writers wrongly expected a lot of water on Venus - "Venus rising from the sea foam"? (Lewis alone suggests a connection between Classical mythology and conditions on other Solar planets.)