I couldn't find an original version of this file, but I had one that had scaling artifacts, because someone thought it was a good idea to scale this image down from 704x480 to 640x480.
I painstakingly fixed the columns that had interpolation in them to end up with this fairly faithful version of the image. The palette should be fairly accurate, but the order could be completely wrong. It is safe to assume that it was created in Extra Half Bright mode.
It looks like the original image had color cycling for the air bubbles, but sadly there was not enough information left to recover the effect.