bagpuddycat: You have to use the guns to make waterless paths out of BOTH sections on the right: top-right and bottom-right. In the bottom case, this involves using the yellow teleport. That's enough hints :)
148: The key at the bottom left is a red herring. With the pair of guns at the bottom centre, you need to fire them left and right to destroy two water squares; the nearby gun next to a guard should be fired upwards.