Hanko to Uusikaupunki by boat: route guide

The fairway crosses the Archipelago Sea from Hanko in the east to Uusikaupunki in the northwest, threading between more islands and islets than any other archipelago on earth. The main route is well marked and carries a nominal depth of at least 2.4 m, which suits most yachts and motorboats.

The route forks at Purunpää, just west of the Kimitoön main island. The inner, eastern branch stays closer to the mainland and the larger islands; the outer, western branch swings around the main islands through more open water. They rejoin north of Iniö, just before Kustavi. Pick the inner line for shelter and shorter legs, the outer line for more open sailing and fewer tight passages.

Navigation is the real work here. The water is shallow and the channels narrow, so follow the marks rather than cutting corners, and expect to slow down in the tightest stretches. There are no tides and no tidal currents, which removes one planning headache. Underwater cables are charted and usually marked ashore and with leading marks; anchor clear of them.

Distances below are the fairway legs, not counting detours into harbours or sidetrips. Treat the times as sailing time at a realistic 4 knots effective speed, which accounts for the slowing and tacking you will do in the archipelago.

The inner route is the shorter and more sheltered option. The outer route adds roughly 20 M (37 km) but gives you more open water and a different set of approaches. Both share the start at Hanko and the finish at Uusikaupunki.

The season runs roughly June to August. That is when guest harbours are staffed, marinas sell fuel and the archipelago villages are open. Fuel is now rare at marinas without a road connection, so plan fills at the mainland and main-island stops.

Midsummer is the busiest weekend of the Finnish boating year; harbours fill and you should arrive early or book ahead where that is possible. Late August still sails well but services start to close. Outside summer, expect cold water, short days and many facilities shut; treat any off-season run as a serious cold-water trip with self-sufficiency.

Weather in the Archipelago Sea changes quickly and the open stretches of the outer route are exposed. Build a spare day into the plan rather than committing to a fixed harbour each night.

Ashore, the guest harbours are the practical base: Hanko, Dalsbruk, Pargas, Turku, Nagu Kyrkbacken, Naantali, Iniö Norrby, Velkua, Kustavi and Uusikaupunki all have at least a grocery store, and most have a wider choice of shops and somewhere to eat. Harbour masters can point you to repairs and local services.

Afloat, you can anchor or land on most islands that look appealing, with three exceptions: protected areas, shores with cottages, and islands with nesting seabirds. Private quays and jetties need the owner's permission, so use guest harbour berths instead.

Cabins, guesthouses and hotels cluster around the larger villages and the Turku–Naantali area; smaller archipelago stops have limited beds, so book ahead in July. If you are sailing, the boat is your accommodation and the harbour fee is your nightly cost.

Charts and a depth sounder matter more than speed here. The main fairway is marked to 2.4 m, but alternatives and sidetrips drop to 2.1 m or 1.5 m, so know which line you are on and check harbour depths yourself rather than trusting a nominal figure.

Language is easy: shipping authorities generally speak Finnish, Swedish and English, and the yachting community is used to visitors. Much of the area is traditionally Swedish-speaking with a large Finnish-speaking minority; Rymättylä, Velkua, Kustavi and Uusikaupunki are Finnish-speaking. Useful chart words: fjärd (selkä) is open water, land is a large island, ö a smaller one, holme smaller still, skär a low island or skerry group, and grund a shallow.

Bring layers and rain gear, a spare anchor line, and enough water and food for a day beyond your plan. If you are arriving from Åland or the open Baltic, join the route at Korpo or Skiftet rather than sailing the whole line from Hanko. Charter boats are available at both Hanko and Uusikaupunki but usually need booking in advance.