Firefighters rushed to the scene near Forthaven to find one houseboat “well alight” and the fire spreading to a second at 11.22pm.
Crews from Lancing and Worthing together with two East Sussex Fire and Rescue Service appliances from Brighton attended along with the rescue boat from East Wittering fire station and officers from West Sussex Fire and Rescue’s (WSFRS) technical rescue unit.
Firefighters wearing four sets of breathing apparatus worked closely with Shoreham Coastguard to tackle the fire, said WSFRS, using a jet and a hydrant.
The last crew left the scene at 1.30am and officers returned at 7am this morning (Sunday) to reinspect.
No one is reported to have been harmed.