Dad has been collecting samples from the rocky planets and has just one more to collect – from their home planet Earth. Taking Cosmo and Sol along, they prepare themselves for a rough landing on the hard surface but... no hard landing. To their surprise, they land in the sea. Before working out how they will get the rocky samples, Cosmo, Dad and Sol decide to go swimming! They splash about, having great fun until an encounter with a seagull gives Cosmo an idea on how to get what they need.