I've used it before swimming and found it worked great, but I'm also not doing a crazy amount of laps, I found when I used it pre-boxing my shoulders get pumped faster yet I can keep pushing more, it doesn't seem to give me a burning out pump kind of feeling, more of a performance pump, if that makes sense.
I think for something like swimming you would be better off with using something like Nitrozine, GPLC and Agmatine Sulfate, GPLC is known to help reduce lactic acid and really give an improvement in muscle endurance.