Pokemon Legends: Arceus — Request 39 Guide (All about Magikarp)

gamerant.com:

Magikarp is well-known in the Pokemon world as being an utterly useless Pokemon… until it evolves into Gyarados at level 20. As such an iconic Pokemon, it's only natural that the Magikarp line would appear in Pokemon Legends: Arceus. Since Pokemon and humans do not coexist in the Hisui region, it's only natural that so many NPCs would know very little — if nothing at all — about Pokemon. If players need a break from Story Missions or catching Pokemon, they can pick up some sidequests to keep busy.

Request 39 is All about Magikarp, and if players haven't caught one yet, they'll need to get one for this sidequest. However, Request 39 takes it a step further by requiring players to complete Magikarp's Pokedex Entry.

As per Pokemon Legends: Arceus' gameplay, entries are not unlocked once a Pokemon has been caught. Instead, players will need to complete a set amount of Research Tasks in order to fill out the entry. Not everyone has the patience to keep Magikarp in the party for long, so here's the quickest way to complete Request 39.

Pokemon Legends: Arceus — The 5 Best Water-Type Pokemon (& Where to Find Them)

Since Magikarp obviously can't be found on land, players will need to have Basculegion to surf across water in order to catch it. Once players have unlocked the Cobalt Coastlands, they can speak to a little girl named Ceci, who's standing near the general store.

She'll notice the Magikarp statues on top of the Galaxy Hall and ask players about Magikarp, believing it to be a very powerful Pokemon. It doesn't matter which dialogue choices are selected here since she'll want to see Magikarp's completed entry regardless. Once this Request is accepted, it's time to work on some Research Tasks.

A school of Magikarp can be found