Activate Pirate Ship by tapping it, dealing 1 damage to any land an opponent controls.
The land dies as a state-based action due to having 0 toughness.
When the land dies, Pirate Ship triggers, untapping Pirate Ship.
Repeat.
You may repeat this loop whenever a land enters the battlefield under an opponent's control.
You may also repeat this loop whenever a creature with toughness equal to 1 enters the battlefield under an opponent's control.
Give Pirate Ship deathtouch, if needed.
Activate Pirate Ship by tapping it, dealing 1 damage to any creature an opponent controls, and destroying it due to Pirate Ship's deathtouch.
When the creature dies, Pirate Ship triggers, untapping Pirate Ship.
Repeat from step 2.
If the effect giving Pirate Ship deathtouch is a static effect, you may repeat this whenever a creature enters the battlefield under an opponent's control.
Results
Destroy all creatures opponents control.
Destroy all creatures opponents control with toughness equal to 1.
Destroy all creatures that enter the battlefield under an opponent's control.
Destroy all creatures that enter the battlefield under an opponent's control with toughness equal to 1.
Destroy all lands opponents control.
Destroy all lands that enter the battlefield under an opponent's control.