I understand that not everyone has the room or budget for a real pool, but even a weekly trip to the YMCA has to be a better alternative than this tethered Swimmer's Treadmill which trades your dignity for fitness.
When fully assembled the pool has a footprint about the size of an SUV, so it's suggested that you can actually set it up in your basement or rec room. But my trust issue alarms go off when I think of 1,500 gallons of water being held back by just a few millimeters of PVC-coated tear-resistant (not tear-proof) polyester.
Instead of using a water jet like those endless pools that keep a current flowing against you, this $1,400 alternative features an overhead rigging that straps you in with an elastic tether keeping you swimming in place. The product shot makes it look like it attaches to the waistband of your trunks, but apparently a harness is actually used so it doesn't yank your drawls off. Still, I'd even risk a swim in the Hudson before adding this to the pile of exercise gear I don't use anymore. [Hammacher Schlemmer]