After posting the things to do in Sandusky, I was reminded of 2 more water parks here in town - Rain (which is associated with Quality Inn and The Thirsty Pony which is a betting parlor) and Castaway Bay which also has a hotel which I listed, and a spa.

At the Thirsty Pony/Quality Inn/Rain water park, there is laser tag as well.

There is Skate World if you like roller skating;

There are 2 museums - the Merry-Go-Round Museum down town and the Maritime Museum, both of which close somewhere between 4 and 5.