While Southron Sailor is engaged with you, each Ship enemy engaged with you contributes its to the total in the staging area.
”There is a great fleet drawing near to the mouths of Anduin, manned by the corsairs of Umbar in the South.”
–Beregond, The Return of the King
Cunning Pirate gets +1 and +1 for each resource on it.
Forced: When Cunning Pirate engages you, discard an attachment you control and place resources on Cunning Pirate equal to that attachment's printed cost.
Forced: When Vicious Marauder engages you, discard a random card from your hand and place resources on it equal to that card's printed cost.
Forced: When Vicious Marauder attacks you, distribute damage among characters you control equal to the number of resources on it.
While you are engaged with Umbar Captain, characters you control cannot attack Ship enemies.
...the strength of the rebels in Umbar was a great peril to Gondor...
–The Return of the King