SWOLF is a measurement of how efficient your swimming is. Normally in a pool it is the number of strokes (left hand ‘splashes’) to complete pool length (metres) + the time in
Is it any good?
Yes, I’d say it is. Try and get it as low as you can by experimenting with different aspects of your stroke, or at least look at the effects on SWOLF of any changes you make.
If you swim in a 10m pool yours will more easily be lower than mine if I swim in a 50m pool (think about it).