Anyone used a Superswim before??

I don't have any Open Water swimming experience but decided to challenge myself and join the Swim Around Key West open water event, with five other friends (2 miles each). I live about 30 minutes from the water so using my pool is probably the most convenient at this point. The only problem... my backyard pool is only 15ft long. After deciding to do the swim I got on the internet and found this "aquatic trainer" (as the manufaturer describes it) online called the Superswim. Has anyone had any experience with it? It was a little over $200. To me, it looks like a fishing pole but seems to provide a decent alternative to the jet pools (which cost over $20k I think). I've only had it for a few days and used it twice for training... I'm just curious about it's ability to build endurance for such a race. Any thoughts are appreciated. The website for Superswim is http://www.superswim.com Thanks in advance