Fossil

Fossil is the ninth episode of the first season, and the ninth episode overall.

Synopsis
"Huge, prehistoric crocodiles still inhabit an underwater cave system the Nektons are exploring. Ant befriends a new hatchling, much to the annoyance of its mother!"

Plot
The Nektons meet with their friend and paleontologist Agnes De-Kretser who believes to have discovered a whole new group of dinosaur fossils. Suddenly a sinkhole opens up causing Will and Agnes to fall in.

As the sinkhole fills with water Will is able to grab Agnes and swim back up to the surface. Agnes explains that the ground surrounding the fossil site is unstable, making it hard to find additional fossils. Believing there to be more fossils in the cave below she asks the Nektons for assistance in finding them. Will deploys the remote mapping pingers to map the sinkhole and the cave to find a way in from the sea.

After Ant retrieves the pingers he puts them all into the new Knight called the Swamp Knight, a Knight designed to operate well on land as well as in the water. Kaiko arrives and gives Ant a new wetsuit, having outgrown his current one (in addition to it smelling funny). Will and Fontaine analyze the mapping data from the pingers revealing three entrances (one of which is too small for a Knight). They all decide to swim in from the top of the sinkhole.

The Nektons swim into the cave where they find a bioluminescent glow coming from the cave ceiling, as well as bats, but most of all a number of fossils similar to the ones Agnes already has. They return to the Aronnax and send some of the bones to Professor Fiction for further analysis. Ant, uncomfortable with his new wetsuit, digs his old one out. Fontaine notices the funny smell coming from Ant's suit, saying it smells like fish food. Ant ignores her and swims to the next cave.

Back on the Aronnax, Kaiko receives a message from Fiction who states that the fossils aren't old at all. Kaiko tells this to Agnes who thinks the mineral content in the water must have petrified the bones prematurely, this leads Kaiko to believe the creatures in the cave could still be alive.

While in the adjacent cave Ant finds an object that turns out to be an egg, which hatches revealing a crocodile like-creature which thinks Ant is its mother. Unable to make contact with any of the three in the caves, Kaiko decides to use the Swamp Knight to reach them. As she gets in a pre recorded message by Ant starts (describing the Swamp Knight's capabilities), upon entering she finds Ant's new wetsuit.

Ant tries to get the baby croc to leave by feeding it fish food which is unsuccessful, so he returns to the other cave, the baby following him. When Ant returns, Will is concerned about the baby croc's size, deducing the mother to be massive. Ant attempts to return the baby to the nest but as he and the others arrive, other eggs start to hatch which attracts the mother. The three are able to hide as the mother passes but one of the babies gets a hold Fontaine's rebreather mask forcing her to leave it behind. The three attempt to escape through the underwater tunnels but realize the caves are all interconnected as the mother approaches. While trying to find another way out Ant's wetsuit gets caught on something, realizing it to be the source of the problem (smelling like fish food) Ant decides to leave it.

Kaiko (through trial and error shown earlier) uses the Swamp Knight's extra strength to clear away the rocks at sea entrance to the caves. Ant, now in his underwear, realizes that living underground for thousand's has made the crocs extremely sensitive to bright lights. The three try make the glow on the ceiling react but are unsuccessful. Suddenly the baby croc appears again which catches the mother's attention. As the mother closes in, Kaiko appears and confronts it. She then launches all the pingers, which makes the glow on the ceiling light up due to the pingers' high frequency. After a brief scuttle the mother throws Kaiko into a pillar knocking her out but Ant steps in and gives the baby croc to the mother, who takes it back to the deeper parts of the cave.

When the Nektons return to the Aronnax they make sure the caves and the surrounding rain forest are placed out of bounds so that any explorers don't find the crocs again. Meanwhile Ant tells the story to Jeffrey.

Trivia

 * Although listed as the 9th Episode, Netflix listed it as the 8th episode of the Season instead. This also apples to The Test where it is listed as the 9th episode on Netflix instead of the 8th.
 * The Swamp Knight's intro message appears again in the later episode The Sunken Gallery.