Hey Joker,
I know where Germantown is because I went to grade school in Menomonee falls. I also used to work for a dive shop out that way back in college.
You've mentioned some nice lakes out that way but be careful about trying to bring a speargun in Lannon quarry- trout are planted there every year and there really isn't much else worth spearing in the place.
I'd be up for going out to Lake Geneva this Sunday- saturday is already fully planned for me by my "honey-do" list.
Lake Michigan can be nice for spearing carp out by the breakwalls- best vis around when the wind is right.
Jon