Väinämeri lies between the Estonian mainland and Hiiumaa and Saaremaa islands. Beining very open and shallow, it is not fun when wind really starts blowing...

"The Väinameri Sea ("the Sea of Straits") is a shallow sea part with an approximate area of 2200 km², where a large number of small islands and bays are located. It stretches between the islands of West Estonia (Saaremaa, Hiiumaa, Muhu, Vormsi) and the mainland. The islands and the mainland are separated by straits: Voosi Kurk, Hari Kurk, Soela, Väike Väin and Suur Väin. In 1894–1896, a 3.6 m long causeway connecting Saaremaa and Muhu was constructed across Väike Väin Strait. Across the eastern part of the Väinameri Sea, earlier known as Moonsund, an important and complicated waterway leads from the Gulf of Finland to the Gulf of Riga. Paternoster — the mediaeval name of Viirelaid Islet located close to the mouth of the Suur Väin Strait — refers to the dangerousness of this waterway.
Koguva Village on the Muhumaa Island Koguva Village on the Muhumaa Island

Shipping lanes leading across the straits were dredged before World War I when a navel port was established in Rohuküla. These were the most extensive works of that kind ever carried out by tsarist Russia. The Väinameri Sea is too shallow for big ships; its mean depth is 5 m, and only the Suur Väin Strait is up to 24 m deep. There is a ferry connection between the larger islands of the Väinameri Sea, as well as between these islands and the mainland. The complicated navigation conditions and the variety of landscapes have made the Väinameri Sea popular among yachtsmen. The main commercial fish in the Väinameri Sea is Baltic herring; perch and garpike are also of some importance. "

http://www.estonica.org/en/Nature/The_Baltic_Sea/The_V%C3%A4inameri_Sea/