The Enchantment Under The Sea Dance was a high school dance that was held at Hill Valley High School on Saturday night, November 12, 1955. It was the dance in which Marty McFly's parents George McFly and Lorraine Baines-McFly fell in love after their first kiss. The entertainment for the dance was Marvin Berry & the Starlighters, and the admission cost for the dance was $1.00.
In the original timeline, Marty's parents attended this dance together after George had been hit by Lorraine's father's car, and Lorraine had nursed him back to health.
After Marty went into the past for the first time, he inadvertently changed how his parents met, with Marty being the one that was hit by the car and attending the dance with Lorraine instead of George. To fix his mistake, Marty formed a plan to make George look like a hero to Lorraine in order to get her to fall in love with him. The original plan was that on the night of the dance, George was to confront Marty in the school parking lot while Marty was in a car with Lorraine.
However, on the actual night of the dance, Biff Tannen made an unexpected appearance and tried to force himself on Lorraine. George, not knowing it was Biff in the car instead of Marty, got roughed up a bit by Biff. Enraged when Biff knocked Lorraine to the ground, George punched Biff, thus standing up for himself and causing Lorraine to fall in love with him. Marty later got on guitar and played "Earth Angel" with the band, but was slowly disappearing from time while doing so. Only when George and Lorraine kissed during the song did he become whole again.
Marty was then coaxed into playing something that "really cooks" and began playing "Johnny B. Goode".