I had to do a quick search for Master Blaster but I'm amazed how accurate your comparison is. Very cool!
With the speed of play, I'll admit that it was an unforeseen problem that now seems quite obvious. I definitely could have dialed back the realism.
As for the little guy, I also agree that he becomes a little useless after a while. I had planned a lot of mechanics involving him that didn't make the cut due to time. For example, I intended to have buttons where you would leave the submarine to weigh a button down, go somewhere as the aquanaut and press another button that allows you to return to the submarine and go somewhere new.
Thanks for playing and giving such in depth feedback! It is greatly appreciated.