The Marine Recruiter acts as a way for you to change to the Marine side when you are on the pirate side without having to quit and rejoin the game. They are found in the Pirate Spawn Island and in Kingdom of Rose, on the bridge's side.
Note: If you change to a marine, you don't lose bounty. It will be saved for when you become Pirate again.
The marine recruiter is a fairly short man who wears the marine uniform, his hair is straight, and colored red/brown.
Recommend becoming a marine for new players because you get faster cheaper ships which is very useful if you don't have the Fast Boat Gamepass.