To Capture A Castle

You are part of an advance guard sent to capture the enemy's Castle.
The Castle is a square construction, built on a square island and surrounded by a square moat.
The Moat is 10 metres wide.
Due to a mistake by the engineers you have scaling ladders to bridge the moat but they are only 9.5 metres long.
You have nothing to use to join the ladders together.
How do you reach the island without getting wet and only using the ladders?