From the area around Kebalviken and the Quality spa and resort area you can take an unmanned cable boat for a small fee. As a hotel guest you will be provided with a special card for this. If you dont use it you will have to walk to the end of a narrow fjord and back out again. It saves you about 30min of walking . You can always get the boat. If it is on the other side just press a button and it will come to your side.
Kosterbåtarna takes people from the harbour in Strømstad and to 5 different locations on the islands of North and South Koster.
We tried the boat in low season and paid 80sek for adults and 60 for school kids.(roundtrip)
You should accept some more in high season.
The ferry departs and arrives at least 5-8 times a day in high season.
The trip to Sandefjord takes about 2,5hrs.
The boats are fully equipped with buffet restaurant,cafe,bar and several taxfree shops.
The company Colorline often offers cheap roundtrip fares that includes a night or two at a hotel. These offers are really hard to beat somewhere else in Scandinavia today.
The price for the crossing is also good. You can fill up your car and get a return trip for as little as NOK 175. Maybe even less if you travel from Sweden.
Their main goal is to get you on board and make you spend your money there.
This is a popular thing to do for families.
Tip: Book the trip on the internet or by phone and make sure to find a departure with the wessel Color Viking. Color Bohus is an older,smaller and a bit outdated ship.
s maybI wrote before the best way to join Stroemstad is by boat, but you can also decide to leave Oslo by train untill this town. I didn't ry swedish train but I think that railways there are as expensive as in Norway. So at the and, take the car! From Svinesund to Stroemstad it takes less than 1 hour (40 km).
By the way here is the address of the swedish railways:
If you have a car, I think this is the best way to know a country, but in Sweden you can also take the train (very expensive in Scandinavia!! )or a big ship (like the boat you see in my pic). If you leave Norway from Sandefjord, near Larvik it's possible to be in Sweden (Stromstad)in 2 hours. You can also decide to take a bus, but it takes many hours...boring ;-)