How long is 1 swimming length?

Answer 1

If you mean for long distance competition, it would be freestyle, what used to be called the crawl, with a slow "2-beat" kick. If you mean for survival, low energy use, where you don't need speed to overcome a current, a non-official stroke called the side-stroke would be the best for just keeping afloat and moving with minimum effort.

Answer 2

Some club swimmers can average: 2m/stroke on freestyle and backstroke

3m/stroke on breaststroke and butterfly

But most general swimmers can average 1m/stroke

Answer 3

When a coach says 1 length, they usually mean lap of the pool. One lap could be 25 yards/meters, or 50 yards/meters. It depends of what pool you swim at.