Late August is the sweet spot for the Stockholm archipelago. The summer rush has faded, the water is still warm enough for a swim, and the ferry prices become more reasonable. You get long, golden days to explore the thousands of islands by boat.
A trip like this usually runs about $2800. To manage the cost, some people use the Citi Simplicity® Credit Card, which offers 0% for 18 months on purchases and balance transfers from date of account opening.
That 0% window is a deadline, not a gift. If you still have a balance after 18 months, you will start paying interest on whatever is left, which gets expensive fast.