A kick to the groin or a twist of the knife is fair game on the open sea.
Dirty Fighting Samples:

Throw Sand
SPECIAL MOVE - Incapacitates all targets in a 90 degree arc 6 yards in front of you for 18 seconds. Taking Damage or Loosing Balance will break this effect. Players and some NPCs are immune to incapacitate.

Twist the Blade
PASSIVE SKILL - Increases the damage of all your cutlass attacks.

Reckless Maelstrom
FINISHING MOVE - Deals 10-25 additional health damage to all hostile targets within 4 yards. Costs 40 initiative, and 40 balance if successful.

Vicious Thrust
BASIC ATTACK - Deals Health damage based on your weapon and causes your target to bleed for 10 damage over 8 seconds.

Grenade
SPECIAL MOVE - An area-of-effect special attack that does 25-40 damage to your target and surrounding enemies.

Vicious Thrust Screenshot