[1rudeboy]

I just don't find it very likely that this effect can "slow down" a swimmer to the point of exhaustion. (And if a swimmer exhausts himself--past the point where he or she should switch to a different stroke--then any drowning becomes attributable to "pilot error").

It's ok to compare a swimmer moving through the water to a ship doing the same. To not consider displacement in the equation is sloppy.

[TalonDJ]

To not consider displacement in the equation is sloppy.
They did not compare them with equations. They did it experimentally.

[Locomotive Breath]

People caught in a rip current exhaust themselves trying to get back to shore. Then they drown. This happens, unfortunately, all the time. Anything that causes a swimmer to make way too much effort to get to a destination would have the same effect. You can claim that their drowning is their own fault but it’s very easy to put yourself in the situation of swimming as hard as you can and getting nowhere and not realizing it until it’s too late.