First, a sea sponge that houses other sea creatures in its pores starts suffering from a mysterious illness. Can Peso figure out the cause of this illness and help this sea sponge? Then, the Octonauts set out to find and photograph Inklin's long lost cousin, the elusive Giant Squid. Will they find him? Shellington and the Octonauts try to track an unusual creature: a jellyfish that can transform from old to young repeatedly - and live forever!