The DVD assumes little-to-no experience with competitive swimming and starts off in the pool citing the need to build confidence in a controlled environment.
Most of us belong to groups and there will always be pressure to keep up. It may be underlying or it may be outright, but no doubt, that pressure to go faster is always there.
Once you caught your breath, it occurred to you that finishing even a short triathlon might be harder than you thought. After a few "laps" you thought, "I can't believe I'm so out of shape."