>>528353522, 3 and 5 are obviously Clefairy, Rhydon and Voltorb respectively. They're also all within the first couple of pokemon by index number, so by that logic 6 is probably Spearow (index 005). 1 is probably just an ambiguous water monster, since they knew it would be used for surf as well. As for the bug I really don't know, the first bugs are Scyther and Pinsir, and it looks like something vaguely between them. Or perhaps the sprite drawings were done before there were any finalised bugs (Scyther is no.26).
So I think realistically:
Surf ride, ambiguous enough that it could be anything
Clefairy
Rhydon
Ambiguous bug
Voltorb
Spearow