Shane Jenkins paddled to the middle of a bay on Long Lake at Nine Mile Falls. His broad shoulders rose from the surface, then his life-jacketed torso and finally the dual jets fastened to his feet, shooting water with the power of more than 150 horses and propelling Jenkins almost 30 feet in the air. This is Jenkins’ second week with the flyboard, a relatively new entry into the world of water sports. Jenkins and his friend, Mike Grytdal, both rural Spokane County firefighters, are offering lessons in their free time after contracting with AV Watersports, based in Bellevue, to offer the attraction in Eastern Washington. For $90, a waiver signature and some brief safety training, thrill-seekers can experience 30 minutes of “flight time” themselves. The equipment has already caused awe on the lake waters among boaters and Jenkins’ neighbors, who are unaccustomed to swimmers rising from the waves like dolphins.