Early astronomers looked to the moon and stars with fascination and imagination. In their minds, it would be hard to imagine that other sphere's would not be much like our own world, and so in the places where the moon appears to be darker, such as Mare Tranquillitatis, the Sea of Tranquility, they assumed that the difference in color was due to water. Of course with the construction of telescopes, they were able to see that there was no water on the surface, but the names remained.
Yep, that's what all the Moon missions were about, seeing if it was feasible to send a fishing fleet there. It didn't work, it seems the minerals on the Moon are slightly different to here on earth and that makes the fish toxic to humans, thats why there is a lot of interest in Mars now.