Timothy Lake Loop, Portland, Oregon - mostly flat, stroll around the Lake with breathtaking views of Mt. Hood and beautiful forests. Be sure to get a look at Little Crater Lake, a small artesian pool near the trailhead.
I'm an avid scuba diver. Ever the domain of the wealthy, scuba diving required both access to the ocean and a shite ton of money for travel & equipment. Not really having any of it, this awesome hobby just kinda passed me by.