Vaping is considered safer than smoking, but no one can really say for sure. I will say my son, who was a "rare" smoker before converting to vaping DID feel his lung capacity improved once he quit vaping entirely. So, that's a "self-reported" study of "one," but if you are a serious swimmer, I don't really understand why you would risk it. Period.
Also the Juul pods are proprietary, so no one knows EXACTLY what is in them. Etc. I mean, it is known that they use Benzoic acid to convert regular freebase nicotine to nicotine salts, and I'd imagine there is some PG and VG in there as well as flavorings, I just don't know what else.
The only thing I can really say is a) vaping is safer than smoking by a fair amount. b) My lungs feel better when I'm vaping, but I'm afraid I already HAVE "old lady smoker lungs." c) In an unknown situation with the POSSIBLITY of some harm (I mean, vaping hasn't been around long enough to study the LONG term effects) and significant benefit for QUITTING (you'll no for SURE you aren't damaging your lungs) well, I'm not entirely sure why you wouldn't QUIT immediately.
The information you want isn't entirely available, and there have been no longitudinal (long term studies of vaping) because it hasn't been around long enough, and there are times when vaping by a never smoker might be useful/advisable/okay etc. I guess, you are a SWIMMER and so I'd err on the side of caution (personally). You don't have to vape so don't.
With that said, it's entirely up to you. If you are a decent enough swimmer to get you on a college team somewhere at some point, I would personally avoid it.
Anna