The quick answer is as little as possible. Space is quite limited, and the weather is pretty reliably warm and mostly dry from Midsummer onwards.
Clothes
Even in summer it may occasionally be cool, especially in June. June can be pretty cold, and some really warm clothing is essential.
Almost anything you bring may get wet, so make sure it will dry easily. Jeans are a bad idea. Several thin layers are best.
A sun hat is essential, as you may be out in the sun for 14 hours, and sunburn is likely. Sun tan lotion is also a good idea, although there should be some on board. We also carry lip salve and after‑sun lotion. A long thin towel keeps water from going down your neck if it gets rough (rarely). A pair of bar towels sewn together is traditional.
We may be able to lend you wet gear, but there’s little choice of size. Better to bring your own, but best if it’s light and fits in a small space. It doesn’t need to be up to Southern Ocean standards, as long as it keeps the rain out.
Shoes must be soft soled, and as non-slip as possible. Most of the deck is bare teak, which is non‑skid, but there are areas of varnish, and when wet this can be like ice to some shoes. The cockpit seats are also varnished, so you can slip getting in and out.
All this needs to be stowed in a small waterproof soft bag. Suitcases will be left ashore! Your personal space measures about 1.8 metres by 1 metre by 50 cm. Coffins are bigger. This space is relatively dry, but water may get in somewhere if it gets rough or we have a thunderstorm.
Please bring your own sleeping bags. A sheet liner for the sleeping bag is essential, although we can lend one if you need it. Pillows are optional, and we carry a selection of small ones with pillowcases.
Safety
Sailing can be dangerous, particularly once out of sight of land (rare in the Baltic). We carry harnesses and proper self-inflating life jackets for a crew of four. Feel free to bring your own.
There are no safety rails on the boat to stop you going over the side (or to trip you overboard). We have safety jack-stays running fore and aft over the working length of the boat. Anyone working on deck in choppy conditions or after dark MUST hook on before leaving the cockpit. Otherwise it’s recommended, but your responsibility.
We carry a life ring, but anyone who goes overboard, even in daylight, may be lost unless they are firmly attached to the ship. Getting someone back on board is not too difficult, thanks to the low freeboard, but we have to find you first. There’s no life-raft, but we tow a wooden dinghy.
Money
Bring enough. Keeping the ship running and the crew fed and watered on board is the skipper’s responsibility. If we eat ashore costs will be shared. Travelling costs at the start and end of the voyage are your responsibility. Sweden stayed out of the Euro and still uses the Kronor (whatever your bank may say), but Finland uses the Euro. The Åland Isles tend to take Swedish and Euro currency. Most places prefer cards, and Sweden is working hard on giving up cash entirely.
Paperwork for non-Scandinavians
A passport is required, make sure it’s not about to expire. The EHIC which used to prove entitlement to free emergency medical treatment in the EU has been replaced post-Brexit by a GHIC which does much the same. See: https://www.nhs.uk/using-the-nhs/healthcare-abroad/apply-for-a-free-uk-global-health-insurance-card-ghic/ for full details. A new GHIC card will take several days to arrive, organise it now. Check any personal medical/travel insurance to see what cover you have abroad. Private medical cover may extend to Europe. The Finnish and Swedish medical services are excellent, but are only available in the larger ports. You will probably have to pay something towards treatment.
If you have relevant certificates of competence, for instance a VHF certificate, or if you’ve passed RYA courses it’s handy to have evidence of that too, but in 20 years we’ve never been asked to produce anything, officials look at the boat and assume we must know what we’re doing.
Health-related matters
Do bring any medication you need. We may well go 2 or 3 days without seeing a shop or a fortnight without a chemist. We carry a small first aid kit, but it won’t cure anything serious. We carry a first aid manual which covers appendicitis and amputation, but the skipper’s had very little practice at either. Warn us if you’re pregnant.
Mosquitoes can be a real plague in Sweden and Finland. If you’re susceptible bring something to discourage them, and something to cure the bites of those who won’t be discouraged.
One also needs to be wary of deer ticks, which live in the longer grass. They may carry things such as Rocky Mountain Spotted Fever, and tick-borne encephalitis which one of our crew caught in 2000. She spent a week in hospital when she got home, and was seriously ill. Your GP may be able to provide an injection to protect against such things. You’re safe away from the long grass, or wearing long wellies! Vaccinations may be available in the UK. You need two, the first at least a month before departure, and a second four weeks after the first. A booster should be given the following year.
They have adders too, but we only see them occasionally, although they do sometimes go swimming.
Things to bring
A sharp knife and shackle key are useful, but pack the knife in hold baggage only; you can’t take it on the plane.
If you wear glasses have something to hold them on. And bring a spare pair.
Bring a good book or three, or the e-book. Some of the time there will be nothing exciting happening, and only one person can steer at once. If you bring a camera have it well protected. Small and inexpensive is best.
Wine and beer are not too expensive, but spirits are, so bring a bottle of your favourite tipple. Buy it at the airport, you can’t take booze (or any other liquids) through security, although you can pack it in hold baggage.