The large ship carried british passengers across the ocean to america. Whats the proper adjective in the sentence?

The proper adjective in the sentence is "British"

Poper adjectives modify nouns and pronouns. In this case, the adjective "British" is modifying the noun "passengers".

Proper adjectives should be capitalized. This type of adjective derives from a proper noun. Example: Britain (proper noun); British (proper adjective).