To start this plan you should be able to swim 1 hour, bike 1.5 hours, and run 1 hour. Over 12 weeks you will increase your weekly volume from about 9.5 hours to 14 hours including 3 swims, 2 to 4 bikes, 3 to 4 runs, and 1 to 2 strength workouts each week. The exceptions are the R&R weeks every fourth week with volume significantly reduced for 4 to 5 days and self-testing at the end of the week to measure progress.
The plan uses common language to describe the workouts and is easy to follow. By the end of 12 weeks you will have excellent Base fitness and be ready to start the Build period 11 weeks prior to your A-priority, half-Ironman race.