Here are the position available in AK Marines. Each Captain can recruit the Lieutenant, Vice-Lieutenant, Petty Officer, Seaman. While The Fleet Admiral and the admiral can recruit any AK members they want and designate them in any position they want.

Fleet Admiral - The rank of Fleet Admiral is carried by only one Marine in the Navy, and is the highest rank within the organization
~ Setsuna13

Admiral - 2nd highest Rank in the Marines (Only 1 marine can hold this title)
- N/A

Captain (Marines) - A captain is the one who commands a ship ( Only 3 marines to hold this title
~ ayisharu
~ angelkatie
~ angelrica

Lieutenant - A lieutenant is somebody who holds a position in the absence of his or her superior.
~ -=CoPiDyeLi=- (Under Captain angelrica)

Vice-Lieutenant - A vice-lieutenant is somebody who holds a position in the absence of the lieutenant or the assistant of the lieutenant.
~ N/A

Petty Officer - They serve as administrative or training personnel and as advisors to the officer corps. However, their most valuable function is as a link between the 'common marines' and the officer.
~ N/A

Seaman - refers to the one of the lowest rates in a navy. It is the common marines.
(Each branch can have up 5 seaman)
~ N/A

Shichibukai - are seven extermely powerful former pirates who have allied themselves with the World Government, hunting down pirates and other criminals. Their job is to help out the Marine's and to watch over whether the Pirates are following the rules and regulations
~ astralgamer
~ Mjhey
~ ExaltedGoddess
~ KiRa
~ spring_onions
~ FeudaLord09
~ N/A