Just so everyone knows, King Boat Festival will take place between October 14 and October 21st in Donggang this year.
On October 14th, not sure what time (it's up to the gods to decide apparently, but seems to be a mid-morning thing), dangki or spirit mediums will descend on the ocean to call in the Thousand Years Grandfather (千歲爺) from the sea. After he comes in - don't ask me how they know, but they do - the entire town erupts in a noisy parade that surpasses even the wildest temple parades in Taipei, with an emphasis on face-painted wangye and 8 generals (bajiajiang). You can also join the mass firewalking (it's not that hot) and see the ship that will be burned at Donglong Temple. You can even make a wish for the god to be burned on the boat.
On October 21st at night they'll bring out the ship and fill/surround it with paper money, wooden wishes and offerings (mostly instant noodles) and burn it on the beach.
If you want to go, make your arrangements now, as hotels are filling up if not already full. It only happens once every three years so if you're into festivals and won't be in Taiwan for three more years, now's your chance.