After you learn Sea Skim from Fuchsia City, your world will open up a bit more. Obviously, you can now travel across the water to reach Cinnabar Island towards the south-west, where another Gym is found. However, there are a few places earlier during your adventure that you can now reach with your new surfing technique.
In addition, you’ve probably noticed that there’s a severe lack of fishing rods in this game. Therefore, besides the rare Squirtle and Krabby etc., you haven’t been able to catch the dozen or so Water-type creatures found in the Kanto region. Thankfully, that’s no longer the case, as you can now use Sea Skim to finally make friends with them!
Those who’ve visited Kanto already will know this, but the Gym after this one is the Fire-type Gym. Now, there’s a very low chance that you don’t have a capable Fire-type counter at this stage in the game. But if you are lacking one for some reason, you should quickly catch and train up a Water-type while you still have the chance.
Use Sky Dash to return to Cerulean City. Near here, there’s a rare item up for grabs. Head north to Route 24 and go across Nugget Bridge. When you reach the end of the bridge, turn left and Sea Skim onto the canal to the left of the bridge. Follow the canal south back towards Cerulean City, then west towards Route 4.
You’ll reach the entrance to the Unknown Dungeon, but access is currently restricted until you’ve defeated the Pokémon League. Land near the entrance, then continue west into Route 4. Keep going along and you’ll reach a PP Max before the end of the ledge. As its name suggests, it raises the PP of a Pokémon’s move to its maximum possible value.
Route 22 or 25
If you want to catch a Poliwag or Poliwhirl, there are two places you go. We recommend flying over to Viridian City and heading west into Route 22. Go to the middle of the route and there’s a medium-sized pond that you can Sea Skim in. Alternatively, you can head to the far end of Route 25 via Cerulean City. There, you’ll find two small ponds to splash around in.
Fly over to Vermillion City next. From the Pokémon Centre, Sea Skim across the water directly below it. You should reach the back of a bench where a Beauty is sitting. Search here for a Big Pearl. Uh, does this belong to the Beauty? Next, head towards the wooden pier to the south of the city, where the S.S. Anne used to be.
Head to the southern-most part of the pier, past Mina. Stand to the right and Sea Skim onto the water on that side. Surf east and you’ll reach a really cool area. It’s the fabled truck where people used to say you could obtain Mew from! That’s just an urban legend, but if you search the bottom-right corner of the truck, there is a Revive.
Exit Vermillion City via the north. As you arrive on Route 6, you should spot a pond up ahead, towards the left side. There are no items this time, but you can catch some unique Pokémon here: Goldeen and, if you’re lucky, Seaking.
Near the centre of Celadon City, to the left of the Game Corner, is a small pond. Sea Skim across it and you’ll reach an Old Man in front of a house. Listen to him rant and you’ll receive TM26 Poison Jab. This is a good Poison-type physical move.
Fly over to Lavender Town next, then exit south onto Route 12. Continue through Route 12 until you’ve gone through the gatehouse halfway along. From there, head south-east along the pier. Then once you’ve gone past the Fisherman, Sea Skim across the water below to reach a lonely island. Here, you can obtain TM24 X-Scissor.
While you’re here, you can also look for Horsea and Seadra swimming around in the water.
There’s quite a few Water-types found by just exploring old places. The more notable ones are Goldeen, Seaking, Horsea, Seaking, Poliwag and Poliwhirl. Of the lot, the Poliwag line is proably the best, because it can eventually become the Water/Fighting Poliwrath.