Manaphy teaches Ditto the move Dive in Pokémon Pokopia’s version 2.0.0 update.
The move became available with the free version 2.0.0 software update. Once Ditto learns Dive, players can swim alongside Water-type Pokémon and build in underwater areas.
This update supports the Bubbly Basin expansion, an underwater town added as the first part of Pokopia’s paid Expansion Pass. The new area introduces underwater exploration, aquatic Pokémon, furniture, and construction possibilities that are not available in the original land-focused gameplay.
Manaphy is the specific Pokémon associated with teaching Dive. It is easy to guess another Water-type Pokémon because several aquatic Pokémon appear in the expansion, but the update’s teaching role belongs to Manaphy.