IMHO, many divers way overestimate the strength of the currents they’re in. It doesn’t take that many knots for things to get gnarly. Light current (to 1 knot); medium current (1 to 2 knots); strong current (2 to 3 knots); very strong current (3 knots); and too strong current (>3 knots). At 2-3 knots, the average diver cannot swim against it or even effectively stop in it. At 3 you get a ripping ride which at best you can only control. Above 3 knots you’re getting into a potentially dangerous situation.
Wickedest currents I've experienced were doing advanced diving off Tobago. Heart Attack Alley & The Washing Machine would tear your mask & fins off if you weren't careful. British Columbia tides and currents can be hair-raising as well.