Referring to the way one shuffles into work/class the day after having spent a full day at the beach, moving a little more slowly than usual because of the excessive use of back and shoulder muscles for water and/or beach sports, the inability to sit or lay comfortably due to the sunburn ranging from irritating to ragingly painful that dictates every move and raises the unnecessary question from everybody of "Did you go to the beach?", and crunchy remnants of sand in the hair, ears, eyes, mouth, or other susceptible body parts even after showering.
Note: A beach hangover can take anywhere from hours to days before achieving a full recovery and may just require a few showers and water, or copious amounts of Aloe Vera and electrolytes.
I spent my entire Labor Day at the beach surfing and chilling with friends, but ended up going to work with a beach hangover the next day.
My cousin was visiting Florida from Minnesota for a week and had a beach hangover her entire stay after spending the first day on the beach.