Shipwreck Channel

From the introduction:

The [player characters] need to cross the channel at the ruined city of Belcamp. Nearly two decades ago, when the city was threatened by the goblinoid forces of the mad wizard Sutar, pirates and sailors attempted to block the channel from invasion by sea. The enemy ships never came. Instead, a pair of white dragons bolted out of the sky and froze the channel. Land forces then rushed in, chasing off the ships’ crews. Many wrecked ships now litter the now unfrozen channel, but a few still float and remain anchored here.