Prescription swimming goggles can be pretty expensive. If you have a spare pair of your regular prescription you can add them to a standard pair of swimming goggles with a packet of Sugru, the hacker-friendly curable adhesive.
Instructables user and Sugru creator projectsugru shares this method of creating DIY prescription goggles: remove the lenses from a set of spare glasses, open the packet of Sugru and knead it into two equal-sized sausage-shaped pieces, place the Sugru "sausage" around the rim of the goggles, and firmly press the lenses into the Sugru.
Make sure there are no gaps between the Sugru and the goggles/lenses and allow the goggles to cure for a few hours before using.
Make your own prescription swimming goggles [Instructables]