The fire was first reported just before 5 a.m. in the 1600 block of West Horizon Drive, according to Mukilteo Fire Department officials.
Several neighbors spotted the fire burning in a boat next to the home. They immediately called 911 and woke up the homeowners to warn them.
By the time fire crews arrived on scene, the fire had spread to the nearby garage, which was attached to the main home. It took 22 firefighters, but they were able to keep the blaze from spreading to the house and eventually extinguish it.
"The quick response and knockdown of the fire prevented further damage to the garage and saved the house from catching fire," Assistant Fire Chief Brian McMahan said in a news release.
The estimated loss is approximately $20,000 for the structure, boat and contents.
Investigators are working to find out was caused the fire.