From Bulbapedia, the community-driven Pokémon encyclopedia.
The Water 1 Egg Group (Japanese: 水中①グループ Underwater 1 Group, formatted as すいちゅう1 Underwater 1 in Pokédex 3D and Pokédex 3D Pro, 水中グループ1 Underwater Group 1 in Generation III and IV guidebooks, and 水中1グループ Underwater 1 Group in Pokémon Stadium 2 and Generation II guidebooks) is one of the fifteen Egg Groups. Like its counterparts Water 2 and Water 3, it is mostly made up of Water-type Pokémon. As of Generation IX, 114 Pokémon belong to this group.
Characteristics
Water 1 group Pokémon tend to be mostly terrestrial Water-type Pokémon, with few fishlike Water types among them. Most are capable of both land-based and aquatic locomotion. It can be thought of as being similar to the Field Group in that it is a "catch-all" Egg Group for aquatic and semi-aquatic animals.
The majority of Pokémon within this Egg Group are capable of breeding with Pokémon of other Egg Groups.
Pokémon
Only in this Egg Group
In this and another Egg Group
Trivia
In other languages