Along with Kril's 69 different shells, also offers several different costumes to equip. While they don't necessarily benefit Kril in gameplay as the shells do, they give the player a way to customize their experience.
Many are clever references to other popular icons that players may be familiar with. Unfortunately, while gives players a Shell inventory that maps out exactly how many they're still missing, there is no such inventory preview for costumes.
Therefore, players can't know when and if they have collected all the available ones, and while a significant portion can be purchased, several are cleverly hidden throughout the map.
When Kril wanders into New Carcinia, the second large area of the game, he will finally have access to shops and services. This includes a shop for stowaways, a blacksmith to upgrade your weapon, and a shop for shells and costumes. While in New Carcinia, Kril will encounter Shellfish Desires, the place for shell and costume shopping, and Shell Insurance.
Seven different costumes are available for purchase here, and all of them will need to be paid for with the game's main currency, Microplastics.