Three adolescent dolphins discovered stranded in a marshy cove at Sandy Hook were humanely euthanized over the weekend after rescuers determined their condition was too dire for survival.

The incident began around 1:00 p.m. Sunday, when a birdwatcher spotted the three Common dolphins trapped deep in the marsh grass near a shallow creek in Spermaceti Cove. National Park Service officers confirmed the sighting and alerted the Marine Mammal Stranding Center (MMSC).

Rescuers from the MMSC mobilized from Brigantine, joining National Park Service staff, certified volunteers, and personnel from Sea Bright Fire and Rescue.

Dressed in dry suits, response teams hiked into the marsh to reach the animals. Each dolphin was placed on a stretcher and carried to the beach for an initial evaluation before being transported roughly half a mile via all-terrain vehicles and a pickup truck to an MMSC rescue vehicle.

The dolphins—identified as one male and two females—were transported to MMSC’s veterinarian for further medical assessment. Experts suspect the trio may be the same dolphins reported swimming in the Shrewsbury River two days earlier on Friday.

Veterinarians found all three dolphins to be weak, lethargic, thin, and in poor body condition. MMSC officials noted that when heavy marine mammals strand on land, gravity exerts immense pressure on their internal organs, causing severe internal damage that drastically reduces their chances of recovery. Given their poor health and the unknown amount of time spent stuck in the mud, rescuers made the difficult decision to humanely euthanize all three to prevent further suffering.

The dolphins were transported to the New Jersey Animal Health Diagnostic Laboratory in Trenton, where necropsies will be conducted to help determine the underlying cause of the stranding.