Because the pilot was never released fully to the public, it was considered lost media for over two decades until being rediscovered by editor Andrew Wilks in July 2023. The pilot runs for about 4 minutes, featuring the marine creatures Cryptoclidus and Liopleurodon hunting in the sea, followed by a Liopleurodon getting stranded on a beach and dying, getting scavenged by Eustreptospondylus dinosaurs as pterosaurs fly overhead. There were also a couple minutes of additional footage, featuring Eustreptospondylus, the long-necked Cetiosaurus and a flock of flying Scaphognathus. Prior to 2023, these additional scenes were the only parts made public on BBC's old website and on the "making of" featurettes of Walking with Dinosaurs (1999) and Walking with Monsters (2005). As these were only test clips, the animals that appear were mostly based on outdated science. Cryptoclidus for example was a 3D scan of a classic 1970s plesiosaur by the company Invicta and the Cetiosaurus had incorrect vertical neck posture and was depicted chewing its food.
This short was meant to be a test episode for Walking with Dinosaurs (1999), and got eventually developed into Cruel Sea (1999) after the series got greenlighted.