Skid sets out to prove that “anything the subs can do – he can do better.” In the process, he borrows some of their things without asking and ends up causing big problems for the subs and Uma who are trying to build a new Substation.

Olly and Beth explore an underground river and discover the secrets of an ancient sinkhole.

Olly wants to prove to Dr. Daniel what a great research sub he is by finding a special artifact for her in the Mediterranean Sea. Only Olly hasn’t yet learned the proper way to retrieve artifacts – and he almost ruins it!

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 has a hard time believing that a grey rock is actually a powerful underwater volcano – but he soon learns that looks can be deceiving and he must rescue a worried crayfish before it’s injured by the eruption.

Skid, tired of always doing the messy work, plays hooky from his job. Knowing Diver Doug will be unhappy with him, he pretends he has been captured by a terrible Sea Creature! When Olly and Beth discover his ruse, they turn the tables on Skid to teach him a lesson.

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 Skid’s careless high-jinks put Shankley in danger, he has to call on Olly and Beth for help – and fast!

While Dr. Kate is trying to talk a salvage operator into leaving an ancient shipwreck untouched, one of the salvaged artifacts goes missing, and Scopes is the prime suspect!

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.