[Northkeep] Good News!!!

[Jerry Herring]

Petty officer is  a non-commissioned rank grade E1 thru E9 just of like a Sergeant is in the Army. 

The lowest ranks going up the chain of command are
Seaman Recruit, 
Seaman Apprentice, 
Seaman
Petty Officer Third Class.

There is a whole series of ranks for petty officers from third class to first class and beyond, the highest non-commissioned officer rank being Master Chief Petty Officer of the Navy.

Hope this helps

Kindly
Ian