Up to 25 firefighters are tackling the blaze at the yacht club in Temple Manor Marsh, Knight Road.
It started at around 8pm.
A fire launch boat and the Coastguard are also at the scene.
More top news
Monday night's weather for the east of the region
Monday night's weather for the west of the region
Three drug dealers have been sentenced to a total of 23 years after admitting they were key players in a multi-million pound drugs ring.