The mistake almost everyone makes
Treating the South Coast like a checklist to clear in one day. Reaching Jökulsárlón and getting back to Reykjavík is possible on paper. In reality it means hours of weather exposed driving, skipping every stop in between, and often finishing in the dark wondering what you actually saw.
The honest choice before you leave: one day for a taste, or two days to actually enjoy it. Everything on this page, fuel, food, sleep, depends on that single decision.
Two safety musts: at Reynisfjara, stay well back from the water, the sneaker waves have killed people. And check road.is and vedur.is the morning you drive. Wind decides this day.