Entermannschaft (Civ4 FFH)
Unlike the Pikeman it replaces, the Boarding Party is not particuarly effective against mounted units; instead, it is best used to take over enemy ships.
The Boarding party is a group of sailors who have a slight talent at leaping from ship to ship, capturing prizes. These Men (and Women) are normal sailors, who find the the riches aboard enemy ships to be so alluring. Besides, they get paid even more.
Most of the Lanun army is conscripted to serve as deckhands at one time or another. Those that show aptitude at sea are trained to be boarding parties, fearless (after enough grog) and deadly (at least on sea) these sea monkeys are ever eager to swing to an enemy vessel and dispatch the crew, claiming the prize for themselves.
Although capable fighters on their own, Boarding parties are also able to attack naval units. And if they win, the naval unit comes under their control.