Heading down to the main quay in Stockholm, I was determined not to board any boat that bore carvings of Roman soldiers and mythological grotesques. I was particularly keen to avoid one that depicted poor Aesacus from Ovid's Metamorphoses, who threw himself into the sea in despair after his beloved died from a snakebite.
I had come straight from the museum where Vasa is displayed, the magnificent battleship of King Gustavus Adolphus of Sweden which sank on its maiden voyage in 1628. It foundered in Stockholm harbour in full view of a huge crowd, which no doubt included the six master sculptors and team of apprentices who had spent two years carving its martial decorations, including Aesacus. Rediscovered in the 1950s, the wreck was painstakingly raised from the seabed and installed in a fascinating museum. But the story of the vainglorious Vasa was perhaps not the most comforting for someone about to embark on a Baltic Sea adventure.
The delights of watery Stockholm had been explored: a fabulous Viking exhibition at the Historiska Museet; the outdoor museum at Skansen recreating 19th-century rural life; the lush food market at Ostermalms Saluhall; a locals' restaurant, Sturehof, not far away serving a velvety lobster soup; the fizzing café life of Södermalm to the south; and the serendipitous discovery of lovely Ivar Los park, in one of Stockholm's oldest harbourside neighbourhoods, affording a panoramic view of the city at sunset.
Churches in both Stockholm and the islands frequently offer summer music programmes. For example, Hedvig Eleonora Kyrka, in a quiet precinct on Storgatan in well-heeled central Stockholm, hosts a number of summer concerts, including one coming up on the last Sunday of August featuring a Swedish invention, "Gregorian lounge music". The acoustics are superb in this mid-18th-century Baroque interior, with its great dome. Somehow, it seemed appropriate for Sweden that when the beautiful young soprano, in the midst of an erotic Rachmaninov song called "Siren", hit the climactic note, her black, gauzy shawl fell to reveal a set of shapely white arms and shoulders. The theatricality seemed perfect in a setting that includes a highly ornate Baroque golden altar, marble pillars and deep-set windows, through which the light was streaming.
But now the time had come to cast off for the island world of the archipelago. After joining the queue at quay 10 at Strömkajen, my anxieties were allayed by the sight of my ferry bobbing beside the dock. Skarpö did not appear dangerously top-heavy, nor did it bear any carved adornments, just the cheerful blue-and-yellow flag of Sweden flapping in the summer breeze.
Furthermore, the omens from my explorations of Stockholm had been encouraging. The fountain sculpture Tors fiske in restful Mariatorget depicted the Norse god Thor triumphing over the sea serpent Jörmungandr. My room in the charming and eccentric Victory Hotel in Stockholm's Old Town was named after Kapten August Svensson, who was reassuringly long-lived (1816-1913). The hotel's owner, Gunnar Bengtsson, has spent his life collecting nautical and especially Nelson-related memorabilia. One of his prized acquisitions is in the lobby of the Victory: a letter from Nelson to his mistress Lady Emma Hamilton. Swedes are not a superstitious lot, so I decided not to read anything into the letter's content, about the weather being too bad to land. Now gazing at the placid sparkling waters on which I was about to embark, it was easy to concur with Nelson that "we must not dwell on gloomy outcomes".
I was the happy owner of a Båtluffarkort, a five-day island-hopper card available from the state-run ferry company Waxholmsbolaget. Of the roughly 24,000 islands in the Stockholm archipelago, scores are served by 21 ferries of various sizes. They have been operating since 1869, when the steamboat arrived and prosperous city folk began to visit the islands for leisure and build summer residences. Whereas Vasa had set sail to wage war, this fleet of ferries guarantees a journey to peace and solitude.
The archipelago is labelled Skärgård on the free "island-hiking" map; the Swedish word skär is from the Old Norse for rocky island and related to our word "skerry". That same map makes it look as though the Baltic Sea between Sweden and Finland has a case of prickly heat, dotted as it is with uncountable islands and islets. Many are virtually fused with the mainland, connected by bridges and buses. But arriving by land would be cheating. On the passenger ferries, it is at least as enjoyable to travel as to arrive. This calm and tideless expanse of sea rivals for beauty any archipelago. Pillowy, billowy clouds somehow bring Valhalla to mind, as seabirds patrol the scudding sailboats.
Chatting to one of the ferry drivers, I was told that those who grow up on these islands have boating in their blood and learn how to navigate the seas from the age of seven. This being Sweden, the sailor in question was not some bearded sea dog, but an attractive young blonde woman, as was her bosun.
Docks and rocks, shady forests and sheltered coves make every passing island look inviting. The island-hopping ticket allows you to disembark on a whim, though if you decide to do this late in the day, it's important to find out in advance whether accommodation is available, or if a later boat will come.
More than three-quarters of the islands in the archipelago are privately owned. This fact would be more off-putting were it not for the astonishing law which Swedes like to boast about – and who can blame them? – of allemansrätten, which gives everyone the right of public access to private land for recreational purposes. You are even permitted to pitch a tent for one night, provided you are not within view of a house. So if you are kayaking round an island, for example, and want to draw up on a beach for a spot of wild camping, you do not have to worry about whether or not it is owned by anyone.
It is great fun planning in advance where to stop over, whether on a busy working island or a back-to-nature retreat such as Finnhamn, once harbour of the Finns. At the further edge of the middle archipelago (about two-and-a-half hours by ferry from the city), Finnhamn is a mini-utopia for campers and hikers. It was acquired by the Stockholm city council in the 1940s so that city children could have access to fresh air and nature, and the island is still in public ownership. The only means of locomotion is walking, and the only accommodation is humble (youth hostel, cabin or camping). The same cannot be said of the only restaurant, the Café-Krog. Before locating the toilet hut through the trees and climbing into my hired sheet sleeping bag, I feasted on fresh fish from the Baltic and a remarkable cheeseboard, courtesy of an artisan cheesemaker on a neighbouring island.
This unlikely combination of the pioneering (rent-a-towel, long-drop toilets) and a first-class restaurant is exactly how the island's charming, quietly spoken guardians, Rolf and Ulla Andersson, like it. In addition to managing the accommodation, shop, restaurant and high-season staff of 40, they oversee an organic farm that provides vegetables and eggs direct to the restaurant.
Most visitors come to Finnhamn to hike, swim and kayak rather than gourmandise. The little island is covered in a web of spongy footpaths that lead past stands of oak and clover meadows full of wild flowers, to reedy inlets and low cliffs of lichen-covered grey rocks, smooth and irresistible for picnics and sunbathing. Luxury yachts cluster in a secluded bay, inevitably called Paradisviken.
Ljusterö is a much larger island with a choice of amenities. As on most of the archipelago, the wooden buildings with barn or gabled roofs, shuttered windows and gingerbread trim are painted in white and the traditional dalaröd (red-brown colour). Commanding a little hill opposite the landing pier at Linanäs stands Rastaborg Country House. The grandmother of the current proprietor, Bosse Pettersson, used to stay at this inn during the summers of her youth, and when Bosse's mother noticed that it was for sale in 1987, she suggested that he investigate. His grandmother's chairs now grace the guests' sitting room and fit in well with the rustic surroundings, including a ceramic cylinder wood-fired stove to keep the bitter winter weather at bay.
When Bosse and his wife, Tina, took on the guest house, they inherited a long-serving member of staff. Now 75, Kerstin used to help her mother lay the coal fires here in the 1940s and is still cheerfully removing dead leaves from the pots of geraniums on the veranda and casting a maternal spell over the place.
Just along from the ferry landing, one of Ljusterö's busy public beaches consists of a pleasant scrap of sand with some sunning rocks and an L-shaped jetty with ladders for swimmers brave (or hot) enough to plunge into the water. A better option is the cliff-bathing place, or badberget, accessed by a footpath between some private houses.
Borrowing a bicycle, I set off to visit a picturesque country church (Ljusterö kyrka) and to explore the island. I haven't had to back-pedal to brake since I was eight. Yet back-pedalling seemed appropriate in this backwater which sometimes evokes the innocence of childhood. If the saddle had not been so high that I had to stand on the pedals most of the time, I would have made it to the nature reserve on the eastern peninsula, where I was assured I would find a pod of seals.
One of the lesser-known perks of the Båtluffarkort is that it entitles you on selected islands in the central archipelago (including Finnhamn) to borrow a publicly owned row boat placed at points where a channel separating two islands is very narrow. Maps of the archipelago include a symbol for "island-hopping rowing boats". The catch is that you have to make sure that the next person who comes down to the dock is not stranded without a boat, so you are requested to tow the borrowed boat back to its starting point.
With the time on my ferry pass ticking by, the comparative V C sophistication of the islands nearer Stockholm beckoned, though they were bound to seem somewhat suburban in comparison. With dozens of boats connecting it to the city only 50 minutes away, Vaxholm is the most popular destination for day-trippers, and provides an appealing stopover on any trip into the archipelago.
It isn't instantly lovable, with its paved ferry landing merging with a roundabout that gives on to a road of tourist boutiques and cafés. However, the old town beyond the tourist information office consists of quiet lanes graced with pretty, wooden summerhouses and quaint mansions, some overlooking the water. The cottages here and lining the cosy north harbour are adorned with gingham curtains, painted mailboxes and bicycles propped against picket fences.
This jolly domesticity contrasts with Vaxholm's main attraction, an imposing offshore fortress which dates from before the Vasa was built, though it has been much changed as its defensive role dwindled and it became a customs house, prison and now a museum.
On the way to the waterside homestead museum, I passed a wooden serving hatch, where I ordered a plate of delicious fried herring and red onion on dark bread. Then I boarded another perfectly seaworthy ferry back to the city. Perhaps Aesacus's fate wasn't so bad after all. According to Ovid, he was metamorphosed into a bird and spent the rest of his days soaring and diving in the sea.
Scandinavian Airlines (0871 521 2772; flysas.co.uk) operates a regular service to Stockholm Arlanda from Heathrow and Manchester and a seasonal service from Edinburgh. Returns from Heathrow start at £132.
British Airways (0870 850 9850; ba.com) flies from Heathrow. Ryanair (0871 246 0000; ryanair.com) flies from Stansted to Stockholm's Skavsta and Västerås airports (both of which are further out from the city centre), and from Prestwick to Skavsta.
To reduce the impact on the environment, you can buy an "offset" through Abta's Reduce My Footprint initiative (020-3117 0500; www.reducemyfootprint. travel).
Route maps and ferry timetables can be found at waxholmsbolaget.se. The Stockholm Island Hopper Card (regular price Skr420/£34) is free with all return SAS flights from the UK direct to Stockholm booked for travel between 1 August and 30 September 2009. SAS passengers can collect their free Island Hopper Card at the Arlanda Visitor Centre in the Terminal 5 arrivals hall daily between 6am and midnight. Customers must present an itinerary when claiming the Island Hopper Card. A deposit of Skr40 (£3.25) is required to obtain the card and will be reimbursed when the card is returned to any of the boat company terminals, on board the boats, or to the Arlanda Visitor Centre.
Victory Hotel, Lilla Nygatan 5, Gamla Stan, Stockholm (00 46 8 506 40 000; thecollectorshotels.se). Doubles start at Skr1,750 (£143), room only.
Rastaborg Country House, Linanäs, Ljusterö (00 46 8 542 40 226; rastaborg.se). B&B from Skr 625 (£51).
STF Hostel Finnhamn, Finnhamn (00 46 8 542 46 212; finnhamn.nu). Dorm beds start at Skr260 (£21), room only.
The summer holiday season in Sweden ends in mid August. After that date, ferries operate less frequently and restaurants open only at weekends until October.
Stockholm Visitors Board: 00 46 8 508 28 508; stockholmtown.com
VisitSweden: 020-7108 6168; visitsweden.com