Rent some ocean kayaks and go out on the big water for a different experience. Otherwise it's like everywhere else, I'd imagine. Big lakes are great for views, freedom, scenery, etc, but if the day is windy, it's going to be worse on a big lake than a small pond.
There's supposed to be some awesome mountain biking in Gorham, but I can't remember where. There are some Maine MTB facebook pages (maybe 207mtb I think it's called) and they can probably offer some suggestions on biking.