|“||When a new dragon is found in Edge Cove, the Dragon Riders must help the Seashocker escape a group of hungry Scauldrons.||”|
- The Seashocker makes its first chronological appearance in this episode.
- Bolt & Float make their debut.
- The Twins practice Loki Day.
Fishlegs and Meatlug are peacefully beach-combing on Edge Cove to see what kinds of things washed up on the beach after the big storm. They later get interrupted when Ruff and Tuff perform two pranks. Much to their displeasure, they continue to stroll to get as far away from the Twins as possible. Fishlegs picks up a nearby rock and is about to toss it to Meatlug, but stops as he hears an uncanny electrical buzzing. His eyes squint as he spots a silhouette of two heads from the lagoon but immediately dismisses the thought thinking it's just Barf and Belch and another one of the Twins' pranks. As he turns around, he sees Ruff and Tuff with Barf and Belch coming out of the fog. Fishlegs turns back towards the open lagoon, but the mysterious creature seems to have disappeared into the water. The Twins run back into the fog bank, leaving Fishlegs to wonder about what he saw.
He comes back to the base to tell the others, but everyone, on account of it being Loki Day, thinks it's just a prank, and as usual, he has to prove it so they would believe him.
While hovering over the lagoon on Meatlug, Fishlegs slings a fish as bait into the water but falls asleep as time passes by. Meatlug starts to drop her altitude as she, too, gets sleepy and tired. As soon as they touch the water's surface, a creature shocks and bolts them awake, thus also causing Fishlegs to fall into the water. While submerged, his assumption is confirmed after witnessing it go after him underwater. As soon as he gets back into the air, he and Meatlug seal the lagoon entrance, locking the creature in the bay to later demonstrate to the others that they are wrong to suspect that he is pulling a prank on them.
Everyone follows Fishlegs to the Cove, still skeptical but eventually become convinced otherwise when the creature jumps out of the water and shocks Snotlout and Hookfang. The gang then realizes that they are dealing with a Seashocker. Hiccup and Fishlegs start to geek out about its type of species, however, seeing how stressed he is, Hiccup tells everyone to destroy the barricade. Hiccup furthermore explains to Fishlegs that it is a deep-sea dweller and therefore must be released so it would reunite with its pod. Despite his friend's remarks, Fishlegs doesn't intend to set the Seashocker free until he examines it fully. The Seashocker gets agitated after a while and jumps out of the water, and Stormfly, feeling attacked, hits the Seashocker with one of her spines. Fishlegs then realizes that he should never have trapped the dragon. While the gang was removing the barricade, he helped the Seashocker to get back to the water, therefore also bonding with him in the process.
When everything looked great, two Scauldrons came to a feeding frenzy, forcing the Riders to battle the pursuing predators for the sake of the Seashocker. Hiccup uses his eagerness and comes up with a plan to save the dragon, but unfortunately, the plan fails. Eventually, the Riders stop trying to repel the Scauldrons as none of them are able to get a clear shot underwater. The Scauldrons follow the Seashocker around, and surround him, causing him to swim into the hole in the ocean floor. Everyone thinks that it is over and starts to head back towards Dragon's Edge, except Fishlegs, who is guilty of prioritizing his needs over the dragon's. All of a sudden, the Seashocker makes a jump over Fishlegs before landing into the water, however, his freedom is cut short as more Scauldrons arrive and begin to head straight towards him. Fishlegs goes to great lengths to save him by throwing himself into the water and teaches the juvenile dragon a trick they have previously discovered. He joins his two heads together, creating a massive electric field across the ocean that shocks the Scauldrons. Afterward, more Scauldrons appear, luckily, his pod comes to his aid and together, they use their electrical shocks to drive off the Scauldrons, and they all swim back into the ocean.
The day ended with a few more pranks, but this time on the Twins' expense. The finale was that their hut was moved to a sea stack near the Edge. The Twins come to the realization that Loki Day is not so great when the tables turn and they are the victims.
- In a part where Astrid and Stormfly move Ruffnut and Tuffnut's hut to a sea stack, Astrid's skirt is missing.
- At the beginning of the episode, Fishlegs mentions all the interesting things that washed up during a recent storm. Though not referenced directly, it's believed the Seashocker was separated from its pod and trapped in the lagoon by that same storm.
- Loki Day is an obvious reference to April Fool's Day, a traditional day of pranking.
- This is the first time different-colored Scauldrons are seen.
- Tuffnut's line, "Creature in the edge lagoon. Just when you thought it was safe to take a bath in a lagoon," is a reference to the horror films Creature from the Black Lagoon and Jaws 2.
- The scene where the Seashocker jumps over Fishlegs is similar to the one from Free Willy.
- Snotlout was never seen getting back at the Twins near the end of the episode.
- The thumbnail of the episode shows a screenshot from Snow Way Out.
- Jay Baruchel as Hiccup Horrendous Haddock III
- America Ferrera as Astrid Hofferson
- Christopher Mintz-Plasse as Fishlegs Ingerman
- T.J. Miller as Tuffnut Thorston
- Andrée Vermeulen as Ruffnut Thorston
- Zack Pearlman as Snotlout Jorgenson