To summarize "Seaside," Lynd begins with recounting the vision of butterflies that swell about the "sandhills" next to the "edge of the sea." He goes on to describe the vegetation that mysteriously "takes root" there. He moves to describing the bathers' tent that fill the plage, or beach, that are occupied by men, women and children dressed in colors as bright as the butterflies and vegetation. He describes their industriousness as their being "exquisitely busy doing nothing" but flying kites, watching birds or playing cricket.
Lynd asserts that only a philosopher can be happy doing nothing. He connects this train of thought to himself and says that in quiet wooded areas, away from the beach crowded with witnesses, he uses a small rubber ball and his wooden walking stick for extemporaneous games of cricket. He notes that the round rubber ball is a "symbol of perfection" that connects the ball-player with the perfection of the "spheres" of the universe.
It is not possible for any man but a philosopher to be indolent and to be happy.
[A person] cannot play marbles without repeating in little the pattern of this universe of spheres.
He expands the concept of being connected with the noble universe to include "shrimpers" who cast nets for shrimp. He notes that folk of all ages engage in this task, all working alongside each other with a sober dedication to the task while "up to their waists at low tide, pushing their great nets before them, ...."
Lynd's thoughts take another philosophical turn as he speculates that it is money that reduces the thrill and dedication of shrimping and other activities to that which is tainted with pleasures destroyed. He contrasts these pictures of pleasures with pleasures parents may (or may not) give their children noting that two years of age is the "sober" age when concentration cannot be broken by seemingly anything. Lynd adds another contrast that describes the sauveteurs (rescuers) of the sea who sound the call of alarm that is the call to safety. He concludes by implicitly asserting his status as a philosopher when he confirms that he can:
loll in the ocean as lazily as on the sandhills, and not even the blasts of the trumpets [sauveteurs] ... can perturb me out of my peace.