(CNN) — A group of four dolphins that was stranded for days in a canal in St. Petersburg, Florida was rescued Tuesday after volunteers formed a human chain to help free them.

The dolphins, including two calves, were trapped in a canal near the Fossil Park neighborhood since Sunday. Experts believe that the height and sound of a bridge nearby acted as a barrier to the dolphins.

"We're able to keep that chain together," said Andy Garrett, a biologist with the Florida Fish Wildlife Conservation Commission. "The dolphins were interested, they actually came over right away, and kind of investigated."

Dolphins use echolocation to navigate in the water. Emitting high-frequency sounds, dolphins interpret the echoes of sound waves that bounce off of objects to find their way around.

When FWC officials were first alerted on Sunday, the dolphins did not appear distressed. Officials waited to see if the dolphins would swim out with the tide.

But after a day passed and the dolphins were still stranded, FWC officials mapped the canal and waterways to come up with a plan to free the dolphins

The rescue team partnered with the National Oceanic and Atmospheric Administration and the Clearwater Marine Aquarium to wade into the canal and herd the dolphins out. Forming a human chain, the rescuers used sounds and vibrations to direct the dolphins into Riviera Bay.