Kanto Route 20

From the rest station, there are three more Trainers, two of which are located very close to each other, before arriving at Cinnabar. There are also two more Trainers along Route 20, one near the western shore of the Seafoam Islands and another just south of the Seafoam entrance on Route 20 in the water.

The length of Route 20 was cut by half in the second generation, which resulted in the number of Trainers being cut to three. Also, the labyrinth of rocks that were present around Seafoam, prohibiting direct access to Route 19 from Route 20 and vice versa, were removed. The only item of interest between the rest station and Cinnabar Island is a lone Trainer southwest of the platform.

Unlike previous generations, Generation III featured no less than four rest islands, two of which contain Trainers. From the rest island present in all generations westward, the route passes north of a small island (with Trainers directly to the north and west of it) before heading south of the largest rest island on the route, north of another small island with a Trainer and north of another Trainer before coming to Cinnabar.

The route is the same in length as Generations I and III. The only noticeable change is that the rest islands from Generation III have combined into a large strip of land that goes along the bottom of the route. There are four Trainers on this island as well as three Swimmers and a Picnicker at the Seafoam entrance. Unlike in Generation II, the barrier that forces the player to travel through the islands' caves remains.

The following Trainers are listed from east to west.

Trainer	Pokémon
East of the islands
Swimmer Reward: 155	Shellder Lv.31 No item
	Cloyster Lv.31 No item
Swimmer Reward: 140	Horsea Lv.28 No item
	Horsea Lv.28 No item
	Seadra Lv.28 No item
	Horsea Lv.28 No item
Beauty Reward: 2100	Seadra Lv.30 No item
	Horsea Lv.30 No item
	Seadra Lv.30 No item
Beauty Reward: 2450	Seaking Lv.35 No item
West of the islands
Jr. Trainer♀ Reward: 600	Tentacool Lv.30 No item
	Horsea Lv.30 No item
	Seel Lv.30 No item
Swimmer Reward: 175	Staryu Lv.35 No item
Bird Keeper Reward: 750	Fearow Lv.30 No item
	Fearow Lv.30 No item
	Pidgeotto Lv.30 No item
Beauty Reward: 2100	Shellder Lv.30 No item
	Shellder Lv.30 No item
	Cloyster Lv.30 No item
Jr. Trainer♀ Reward: 620	Goldeen Lv.31 No item
	Seaking Lv.31 No item
Beauty Reward: 2170	Poliwag Lv.31 No item
	Seaking Lv.31 No item

The following Trainers are listed from west to east.

Trainer	Pokémon
Swimmer♂ Cameron カツヤ Katsuya Reward: 272	Marill♂ Lv.34 No item
Swimmer♀ Lori ケイ Kay Reward: 640	Starmie Lv.32 No item
	Starmie Lv.32 No item
Swimmer♀ Nicole クニミ Kunimi Reward: 640	Marill♀ Lv.29 No item
	Marill♀ Lv.29 No item
	Lapras♀ Lv.32 No item
Trainers with a telephone symbol by their names will give their Pokégear number to the player, and may call or be called for a rematch with higher-level Pokémon.

The following Trainers are listed from east to west.

Trainer	Pokémon
East of the islands
Swimmer♂ Barry ガクジ Gakuji Reward: 124	Shellder♂ Lv.31 No item
	Cloyster♂ Lv.31 No item
Swimmer♂ Darrin テルユキ Teruyuki Reward: 112	Horsea♂ Lv.28 No item
	Horsea♂ Lv.28 No item
	Horsea♂ Lv.28 No item
	Seadra♂ Lv.28 No item
Swimmer♀ Shirley アサミ Asami Reward: 120	Seadra♀ Lv.30 No item
	Horsea♀ Lv.30 No item
	Seadra♀ Lv.30 No item
Swimmer♀ Tiffany ハルコ Haruko Reward: 140	Seaking♀ Lv.35 No item
West of the islands
Picnicker Irene ミズキ Mizuki Reward: 600	Tentacool♀ Lv.30 No item
	Horsea♀ Lv.30 No item
	Seel♀ Lv.30 No item
Bird Keeper Roger トモヒコ Tomohiko Reward: 720	Fearow♂ Lv.30 No item
	Fearow♂ Lv.30 No item
	Pidgeotto♂ Lv.30 No item
Swimmer♀ Nora リリカ Ririka Reward: 120	Shellder♀ Lv.30 No item
	Shellder♀ Lv.30 No item
	Cloyster♀ Lv.30 No item
Swimmer♂ Dean レツジ Retsuji Reward: 140	Staryu Lv.35 No item
Picnicker Missy クミコ Kumiko Reward: 620	Goldeen♀ Lv.31 No item
	Seaking♀ Lv.31 No item
Swimmer♀ Melissa メグミ Megumi Reward: 124	Poliwag♀ Lv.31 No item
	Seaking♀ Lv.31 No item
Rematch
Swimmer♂ Darrin テルユキ Teruyuki Reward: 208 After delivering Sapphire to Celio	Seadra♂ Lv.52 No item
	Seadra♂ Lv.52 No item
	Seadra♂ Lv.52 No item
	Seadra♂ Lv.52 No item
Picnicker Missy クミコ Kumiko Reward: 700 After becoming Champion	Seaking♀ Lv.49 No item
	Seaking♀ Lv.49 No item
Picnicker Missy クミコ Kumiko Reward: 1080 After delivering Sapphire to Celio and defeating the previous team	Seaking♀ Lv.54 No item
	Seaking♀ Lv.54 No item
Swimmer♀ Melissa メグミ Megumi Reward: 196 After becoming Champion	Poliwhirl♀ Lv.49 No item
	Seaking♀ Lv.49 No item
Trainers with a Vs. Seeker by their names, when alerted for a rematch using the item, may use higher-level Pokémon.

The following Trainers are listed from west to east.

Trainer	Pokémon
West of the islands
Swimmer Frankie カツヤ Katsuya Reward: 704	Azumarill♂ Lv.44 No item
Bird Keeper Bert マスミツ Masumitsu Reward: 1376	Wingull♂ Lv.46 No item
	Fearow♂ Lv.43 No item
Swimmer Mina チグミ Chigumi Reward: 656	Luvdisc♀ Lv.38 No item
	Luvdisc♀ Lv.39 No item
	Luvdisc♀ Lv.41 No item
Picnicker Cheyenne アサミ Asami Reward: 720	Shinx♀ Lv.45 No item
Bird Keeper Ernie ヤジロウ Yajirō Reward: 1536	Starly♂ Lv.48 No item
Swimmer Leona リオナ Leona Reward: 704	Bidoof♀ Lv.44 No item
Picnicker Adrian ナナカ Nanaka Reward: 720	Shroomish♀ Lv.45 No item
East of the islands
Swimmer Luis トシミツ Toshimitsu Reward: 672	Seadra♂ Lv.46 No item
	Quagsire♂ Lv.42 No item
Camper Pedro シンヤ Shin'ya Reward: 720	Linoone♂ Lv.45 Sitrus Berry
Swimmer Elmo シブキ Shibuki Reward: 672	Poliwhirl♂ Lv.46 No item
	Tentacruel♂ Lv.42 No item
Swimmer Lori ケイ Kay Reward: 672	Starmie Lv.42 No item
	Starmie Lv.42 No item
	Starmie Lv.42 No item
Swimmer Nicole クニミ Kunimi Reward: 672	Marill♀ Lv.39 No item
	Marill♀ Lv.39 No item
	Lapras♀ Lv.42 No item
Trainers with a telephone symbol by their names will give their Pokégear number to the player, and may call or be called for a rematch with higher-level Pokémon.

The following Trainers are listed from east to west.

Trainer	Pokémon
East of the islands
Swimmer Douglas タツオ Tatsuo Reward: 820 3 Poké Balls	Gyarados♂ Lv.42 No item
Swimmer Darrin テルユキ Teruyuki Reward: 880 3 Poké Balls	Golduck♂ Lv.44 No item
	Gyarados♂ Lv.44 No item
Beauty Shirley アサミ Asami Reward: 820 3 Poké Balls	Wartortle♀ Lv.41 No item
	Starmie Lv.41 No item
West of the islands
Picnicker Irene ミズキ Mizuki Reward: 860 2 Great Balls	Marowak♀ Lv.43 No item
	Gloom♀ Lv.43 No item
	Wigglytuff♀ Lv.43 No item
Beauty Hansol ナツミ Natsumi Reward: 860 3 Poké Balls	Slowbro♂ Lv.43 No item
Bird Keeper Roger トモヒコ Tomohiko Reward: 2,700 3 Poké Balls	Fearow♂ Lv.45 No item
	Dodrio♂ Lv.45 No item
	Pidgeot♀ Lv.45 No item
Swimmer Dean レツジ Retsuji Reward: 880 3 Poké Balls	Starmie Lv.44 No item
	Tentacruel♀ Lv.44 No item
	Kingler♂ Lv.44 No item
Picnicker Missy クミコ Kumiko Reward: 820 2 Great Balls	Jolteon♀ Lv.41 No item
Beauty Nora リリカ Ririka Reward: 820 3 Poké Balls	Cloyster♂ Lv.41 No item
Beauty Melissa メグミ Megumi Reward: 860 3 Poké Balls	Seaking♂ Lv.43 No item
	Jynx♀ Lv.43 No item
Ace Trainer Marty ショウ Shō Reward: 4,600 5 Ultra Balls	Golem♂ Lv.45 No item
	Pinsir♂ Lv.46 No item

In the first appearance of this route, the rock boundaries follow a strict path. Rocks blocking the way, forcing people to travel through the Seafoam Islands. There are two signposts numbering the islands, one outside each cave. There is also a wooden pier-like island in the west section.

The route is shortened by nearly 30%. The west island doesn't have an entrance, and the cave of the east one is now Blaine's gym. Due to this, the rocks blocking the water path are removed, and there is just one signpost, indicating the Gym and the Gym Leader.

In Generation III, the rock formations are not straight, making the route seem more natural. The Seafoam Islands are remodeled and made bigger. The characteristics of the Seafoam Islands are essentially that of Generation I. The west island is now a tiny sandbar, and three other sandbars are added near the original.

In this generation, the route is very similar to its appearance in Generation III. Unlike Generation II, the path is blocked again and the player is forced to travel through the cave, but the Cinnabar Gym is still in the east cave. Now one signpost indicates the landmark's name, and the other has the Gym information. The four tiny islands in the west are now merged into one large sandbar in the southwest section, with some Trainers on it. Several rocks are now present in the middle of the route.

Route 20 made a brief appearance in the beginning of Holy Moltres, where Red was seen arriving at Cinnabar Island on his Gyarados after having visited the Seafoam Islands.