Being on summer vacations is like sailing through calm, tropical waters: letting the wind, the tides and the sun lead you wherever you might go. Enjoying the companionship of your crewmates (Mao and Peter) and the friendly sea-creatures you pass (friends and family), whilst avoiding shark-infested waters (thinking about back-to-school.)
Going back to school is like having to return to some sordid port on a small, polluted, overcrowded island... with pirates. And cannibals. Slogging your way through ten landlocked months with only your trusty ship-mates to keep you from trying to keelhaul yourself.
And here the metaphor dies.