With the boating season here, the Danbury Fire Department is offering some safety tips on how to be prepared for an onboard fire.  FEMA officials say fires that occur on boats or in marinas can spread quickly and present unique response challenges.  Boaters are urged to have a fire emergency plan and practice it.  Only certified chargers should be used for personal electronic devices, and boaters are cautioned not to overload power outlets.  Appropriate fire extinguishers should easily accessible, and all boaters should be trained on how to use them.