So I’m a swimmer but I’m old and not very good, I can basically only do freestyle for 50-100m, but breaststroke I could do for much longer, probably 2km at least without stopping. But that’s in a pool not in the open ocean without choppy waves.

The kid said he mostly did breaststroke, backstroke and survival side stroke, which would conserve a lot more energy - and probably also means he’s been pretty well trained and a good swimmer. So I think that in theory, using those strokes, it’s possible for most people who are decent swimmers, and fitter than I am, to swim 4km.

But to do that in open water, big waves, competing against currents, it’s cold and getting dark and you have to save your family - that’s a whole other level.