Swedish maritime archaeologists have discovered two wrecks believed to be 17th-century warships, at least one of which is likely to be the sister ship of the Vasa, a historic vessel that sank on its maiden voyage.

“When I came down as the first diver ... I saw this wall five or six metres high and I came up and there was a massive warship,” the maritime archaeologist Jim Hansson said. “It was a thrilling feeling.”

The two wrecks were found in the Swedish archipelago outside the town of Vaxholm in a strait leading into Stockholm.

Vasa, named after one of Sweden’s kings, was a 69-metre vessel equipped with 64 cannons. It was meant to have been a symbol of Swedish military might, but capsized and sank less than a mile into its maiden voyage in 1628.

The ship was salvaged in 1961 and is on display at Stockholm’s Vasa Museum, one of Sweden’s most popular tourist spots.

Three other ships – Applet, Kronan and Scepter – were ordered from the same shipwright, and all served in the Swedish navy and participated in battles.

“We think that some of them were sunk in the area,” said Patrik Hoglund, another maritime archaeologist and diver at the newly established Museum of Wrecks. They are believed to have been sunk deliberately when they were decommissioned, serving as underwater spike strips for enemy ships.

The divers took samples of wood samples from the latest wrecks to be discovered, which will be sent to a laboratory for dating. “Then we can even see where the timber has been cut down and then we can go back and look in the archives and I think we have good chances to tell exactly which ship this is,” Hansson said.

Despite being centuries old, the wrecks, like the Vasa , are in fairly good condition, thanks to the brackish waters of the Baltic Sea. “We don’t have salt water and some organisms that live in other waters don’t exist in the Baltic, so it is very well preserved generally in our waters,” Hoglund said.

There are currently no plans to salvage them, because they are better preserved at sea.