If you have been taking classes from a Total Immersion coach or if you have been using the drills contained in the TI Effortless Endurance Self-Coaching Course
, this will provide a good foundation for any kind of swimming, including open water swimming.
For swimmers who have been practicing the TI training program for awhile and who are ready to move into open water swimming, there is a DVD called Outside the Box
which deals with the particular issues you will face when you do this. (The "box" is the swimming pool.):