San Diego Fire-Rescue Department were called to Harbor Island where a boat reportedly caught fire around 10 a.m.
The 46-foot boat was far from a water supply, so firefighters laid 2,100 feet of hose to reach the fire coming from inside a 3-by-3-foot hold, an area where equipment like electrical components and fuel tanks are generally stored, according to Battalion Chief David Connor.
Access to the fire's exact location was difficult because of the small, smoky hold's unknown contents, Connor said. Firefighters knocked down the fire in about 30 minutes.
The boat's owners were not onboard and no injuries were reported, SDFD said.
Investigators were working to determine an exact cause.
Harbor Police also assisted in the incident, bringing boats capable of pumping sea water into a hose.