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Into the Jaws of Death
Dangerous Seas is the first episode of Sea Monsters, and the third episode in the Chased by... series overall. It first aired on 9 September 2003.
The Seventh Most Deadly Sea
After the introduction, Nigel Marven looks at the Time map, a long map that shows a timeline of prehistory. Nigel, on his quest to visit the seven deadliest seas ever, goes to his first destination, the Ordovician, a world of creepy-crawlies and an alien atmosphere.
Nigel, walking through a barren landscape with an oxygen tank containing a special air mix, says that the air during the Ordovician is atrocious and that if he wasn't prepared with his breathing equipment, he would feel rather sick and would get bad headaches. Due to the presence of high levels of carbon dioxide, plants are not able to grow so no animals live on the land. However, in the water, it was completely different story.
Later, Nigel walks along the shore searching for bait. As no animals live on the land to scavenge on whatever the sea churns up, the corpses remain festering. Nigel uses a fork to pick up an Astraspis - an armoured-plated fish, and enters the water.
About waist-deep in the Ordovician waters, Nigel finds a silhouette under the water. He frantically tries to grab the figure and once he does, it turns out to be a Megalograptus. As the sea scorpion begins to struggle to free itself, Nigel says that he has to stay clear of its pincers.
Nigel chucks the Megalograptus back into the water, where it feeds on the Astraspis Nigel used to tempt it. After completely shredding the bait with its pincers and mandibles, the sea scorpion turns on Nigel and starts to bite his leg. Nigel quickly retreats to the shore and remarks "another scar for the collection".
Later, Nigel finds a large Trilobite corpse on the shore. Nigel says that small bait would not be useful in finding some of the larger sea monsters in the Ordovician seas. Nigel then decides to fit a camera onto the Trilobite. However, in order to do that, he needs to pop out on of its eyeballs. As Nigel fits the camera in, the cameraman turns away in disgust.
As the sun sets, Nigel realises that in Ordovician times, the Earth rotates faster and rather than the usual 24 hour-long day, an Ordovician day is 21 hours. Nigel and his crew then decide to sleep.
The next day, Nigel is in his speedboat. He is equipped with a diving suit which had a special breathing tank attached. Due to the atmosphere, if he dives wearing a normal diving suit, he would become unconscious. He is also equipped with a bite-proof shark suit suit which would protect him from the Megalograptus. He pushes the boat into the water.
Sailing above deep water, Nigel decides to deploy the Trilobite cam into the water. Watching the live footage, Nigel sees a Megalograptus approaching the Trilobite to feed. However, Nigel manages to repel it by knocking it off.
In the late afternoon, Nigel sees a large, tentacled creature feeding on the Trilobite cam. While trying to reel in the camera, the creature takes out the camera, leaving Nigel's monitor as static. Nigel quickly suits up and dives into the water.
Following the trail left behind by the camera, Nigel finds out that the predator had eaten the camera. Meanwhile, by Nigel, a group of Megalograptus gathers. This confuses Nigel. When he looks up, he finds the predator - a Cameroceras.
As the orthocone sees him and approaches him, Nigel starts to panic and flashes his torch at the animal's simple eyes to deter it. It works and the orthocone swims off. When the Cameroceras left Nigel's sight, he turned his attention onto the Megalograptus. Suddenly, to Nigel's surprise, the orthocone reappears and swiftly kills one of the Megalograptus. Nigel watches as the Cameroceras penetrates the sea scorpion's carapace with its beak.
The Cameroceras then moves on to another Megalograptus and kills that one too. As it swims away, Nigel quickly grabs onto its shell and hitches a ride. However, after some time of riding, Nigel realises that the orthocone is pulling him deep into the water and lets go before returning to the shore.
As Nigel returns to the shore, he finds out that the Megalograptus are gathering to reproduce. Nigel quickly makes a run for the shore and tosses some of the sea scorpions away. As he reaches the shore, some of the Megalograptus climb onto his speedboat. The episode then cuts to the Time map and travels forward in time to the Triassic.
The Sixth Most Deadly Sea
As Nigel enters the Triassic, a Coelurosaur runs past him. While the pterosaurs rule the skies, the dinosaurs have just appeared. However, in the seas, marine reptiles are at the top of the food chain.
As Nigel dives into the water, he finds a pair of Nothosaurus. The inquisitive marine reptiles investigate Nigel who has the prod at the ready. As the pair circle him, Nigel decides to grab onto the jaws of one of them and has a prehistoric ride. Soon after, he lets it go to breathe.
Moments after, Nigel finds a bizarre-looking reptile called Tanystropheus walking on the sea floor. This reptile is characterised for its incredibly long neck and tail. Nigel approaches the reptile and grabs onto its tail. As the Tanystropheus tries to escape but accidentally gets its tail torn off. As the Tanystropheus swims away, Nigel continues to hold the spasming tail.
Out of nowhere, a large marine reptile snatches the Tanystropheus tail from above. It was a Cymbospondylus. As it swallows the tail whole, it approaches Nigel. As it circles him, it makes a mock charge. Spooking Nigel, he decides to use his electric prod on the Cymbospondylus and pokes it with it. As the ichthyosaur approaches again, the episode cuts to the Time map which goes back in time to the Devonian.
The Fifth Most Deadly Sea
In the seas of the Devonian, a crew member of The Ancient Mariner Mike, made a reconnaissance dive to see if he could capture any footage of Devonian marine life. Apparently, he has struck gold on the first dive, claiming he got close-up footage of a Dunkleosteus. Nigel and the crew watch the recording and quickly identify the Dunkleosteus.
Soon after, the crew begin to assemble a round shark cage and Nigel tries to fish for some bait. He manages to catch a Bothriolepis - a relative of Dunkleosteus. He then wraps the placoderm in chainmail as part of a bet to see if Dunkleosteus can bite through it.
Once the cage is built, Nigel and the cameraman swim into it with the bait. However, rather than a Dunkleosteus appearing, a Stethacanthus - a primitive shark - arrives. As it circles the cage, it quickly swims away as if it detected something dangerous.
To Nigel's pleasure, the creature is a Dunkleosteus. As it swims past the cage, Nigel explains that its jaw extensions act like shearing plates to grind through armour. As he tempts the giant fish with the bait, it begins to bash the cage. As the tension peaks, the Dunkleosteus accelerates towards the cage.To be continued...