I am pretty sure that all patches come from one or two manufacturers who make he base material and the adhesive. The pharmaceutical companies ad the medication in forme of a micro encapsulated mass into the adhesive.
The adhesive is a version of pressure activated adhesives which reach their maximum adhesion by the initial pressure applied to them. If the substrate they are applied to is not clean (free of any contamination), the adhesion may fail. The adhesion will be reduced if the adhesive gets cooled below the targeted application temperature (which, for these patches, is the average temperature of the human body).
The conclusion is that water may coo, down the adhesive to much and bubbling will result (the idea of transdermal delivery of medication was originated in our labs).
I hope that this answers the question about swimming with these patches!