Yeah man, neither of these looks particularly Aquaria-esque to me...that poster image uses a similar angle to the Aquaria poster, but c'mon, that's a pretty tenuous connection. I did a painting six years ago involving the sun viewed at a similar angle that doesn't have anything to do with Aquaria either.
BREAKING NEWS: SOURCES INDICATE THAT, SOMETIME PRIOR TO 2007, SOMEBODY MADE A GAME SET UNDERWATER, ALSO ANOTHER GUY MIGHT'VE DRAWN A PICTURE OF THE SKY IN PHOTOSHOP USING SINGLE-POINT PERSPECTIVE.