After accidentally swallowing a mobile phone, William, a blue whale, and Reuben, an eco-lobster with one claw, receive an unexpected call from the owner, Clara. They discover why the phone is important and decide to return it personally.With a thousand miles to swim in three days, the two friends are forced to navigate dangerous waters. Things quickly go from bad to worse as fierce storms, a hungry octopus and destructive bottom trawlers stand in their way. With time running out and Blackheart's sea wolves hunting them, they will have to work together and face their fears to succeed, but even that might not be enough as the crew of the Hoeruhanta is waiting?