During the episode "Shock and Awe", a Seashocker named Bolt & Float was separated from his pod and ended up within the Edge Cove. Fishlegs, in his extreme eagerness to study the dragon, used Meatlug's lava blasts to barricade Bolt & Float in the cove, preventing him from leaving. Upon returning with Hiccup and the other Dragon Riders, however, Fishlegs realized that Bolt & Float was agitated and attempting to escape his confinement. Hiccup and the others attempted to destroy the barricades while Fishlegs befriended Bolt & Float.
However, due to the series of explosions caused by the other Dragon Riders' dragons, a pack of Scauldrons were attracted to the cove, hoping to eat Bolt & Float. However, after a lengthy chase and with the help of the Riders distracting the Scauldrons with electric eels, Bolt & Float was able to escape from Edge Cove. The Scauldrons were eventually chased off and Bolt & Float returned to his pod.
Possible rewards include: Runes (in-game currency), Collection Items for other game activities, Rare "Card" Packs, and Fish resources. Dragon Eggs can also be found of the Covecharger, Seashocker, Scauldron, or Tide Glider.
Edge Cove is also mentioned in Bolt & Float's description.
Fishlegs' love of studying got this Seashocker trapped in Edge Cove. Fortunately, Fishlegs is a fast learner, and was able to help free the Dragon before it was too late.