A few years ago, researchers in Miami discovered through a series of experiments, that if they dropped a hydrophone into the water and recorded the clicks/reflected clicks of a dolphin using echolocation to visualize its environment and then played the audio back to other dolphins, those dolphins could identify objects with 92% accuracy. 

This is an impressive find because it implies that since dolphins can interpret the echoes of one another's clicks to construct the same mental representation, they're effectively able to communicate what they're seeing with other members of their pod as they're seeing it. 

After discovering this, the research team led by Jack Kassewitz (speakdolphin.com) set about trying to see for themselves what the dolphins were seeing. To do this, Kassewitz contacted a UK acoustics researcher, John Stuart Reid, inventor of the CymaScope. 

Raw Story - This picture reveals how dolphins communicate — and how we may some day understand their language 

One of the scientists, Jim McDonough, submerged himself in front of the female dolphin “Amaya” in a pool at the Dolphin Discovery Center in Puerto Aventuras, Mexico. 

He exhaled all the air from his lungs to overcome his natural buoyancy and to avoid bubbles from a breathing apparatus, and the dolphin directed her echolocation at McDonough. 

Other researchers then used high-specification audio equipment to record the dolphin’s signal, and they sent those recordings to the CymaScope laboratory in the United Kingdom. 

Acoustic physics researcher John Stuart Reid first made two-dimensional images from these recordings and then used photo analysis to extract data and three-dimensionally imprint the signal onto a water membrane. 

The process revealed dolphins relay “quasi-holographic properties of sound” as their echolocation reacts with water, Reid said.

From the SpeakDolphin press release 

The CymaScope’s patented imaging process imprints sonic vibrations on the surface of ultra pure water. Reid explained, “When a dolphin scans an object with its high frequency sound beam, each short click captures a still image, similar to a camera taking photographs. Each dolphin click is a pulse of pure sound that becomes modulated by the shape of the object.” In this case, Reid used the echolocation recordings to capture clearly identifiable 2D images from the experiment, which included a flowerpot, a cube, a plastic “+” symbol, and a human being. 
Kassewitz then turned to 3D Systems, inventors of 3D printing and global leaders in 3D digital design and fabrication, to transform 2D image data into a 3D-printable. vrml file. The files were then brought to life using 3DS’ Projet 660 printer, allowing the objects to be printed rapidly in full color and retaining the initial Cymascope image characteristics. 

“We were thrilled by the first successful print of a cube by the brilliant team at 3D Systems,” said Kassewitz. “But seeing the 3D print of a human being left us all speechless. For the first time ever, we may be holding in our hands a glimpse into what cetaceans see with sound. Nearly every experiment is bringing us more images with more detail.” The team’s next goal is to find out if and how dolphins may be sharing these echolocation images as part of a sono-pictorial language.

The team plans to publish their research in an forthcoming paper and a documentary about their work is already in development.