Nah, you’re wrong here. Let’s keep it simple. Assume the lane is 30m long. A swimmer can swim at 10m/s, but there is a 5m current one way in his lane. A swimmer with no current has to swim 60m total (30 there, 30 back, we’ll ignore flip time), and that’ll take 6 seconds at 10 m/s. In the lane with the current the…