The subs help a pod of Baltic Sea grey seals find a new iceberg home… but then they can’t get rid of the grateful seals, who follow them around disrupting their work!

Olly’s “sub” conscious tells him that he might not be ready to pass an important obstacle course test.

In need of attention, Skid cries out that Brandt is in danger. When his friends realize they’ve been fooled, they ignore Skid’s genuine cry for help, with potentially catastrophic results.

Olly and Beth set out to retrieve a downed satellite but Dirk beats them to it. Meanwhile, because of their love for old sci-fi movies, Skid, Brandt and Bobsie are convinced that the satellite has returned to Earth with more than just scientific information aboard.

While on a deep sea adventure Olly discovers many strange phenomena, including a disappearing shipwreck and some interesting deep sea fish.

The subs join Dr. Kate at the opening of the Shanghai Marine Museum. Skid joins them, but soon feels left out as Walter and the subs reminisce together.

Olly finds the "perfect shell" and can't wait to add it to his seashell collection. But an old hermit crab has different plans for it.

When Scopes removes an ancient Roman urn from the seabed he causes trouble for everyone.

Olly and Beth are in the Caribbean Sea looking for one of Christopher Columbus' sunken ships when Olly is almost sucked up in a beach dredging pipeline. The dredger uncovers an old anchor in the sand. How can the subs stop the dredging and protect the site?

Beth takes inspiration from ancient fish traps to go one better than Olly when something of Dr. Daniels’ needs recovering.