When Elliot and Sean are talking at the aquarium next to the dolphin you can see she's already wet before it even splashes her.
The unlabeled urine sample Carla finds and attempts to identify would never be accepted for lab testing by any hospital's protocol. Once a biological specimen's owner cannot be determined the sample is discarded to avoid mistaken diagnoses. (With the exception of very invasively collected specimens like cerebrospinal fluid, which requires doctor sign off).