Bays that are shallow far out into the sea, with fine sand and clay, are rare in Hordaland. Where they are found, the reason is usually that the edge of the glacier made smaller advances or stopovers when it calved back at the end of the last Ice Age. This is what happened at Vinnesleira.
At the bottom of the Osa fjord there is a cultural landscape marked by great contrasts; the wide terraces and the river delta at the fjord contrast with the steep hillsides in the background, where Norddalen leads up to the mountain. There are two farms here. Osa and Sævartveit – the farm at the river mouth and the hollow by the sea.
When the lush beach area innermost in Ulvikapollen was protected, the bird life was instrumental to the decision. The plant diversity is just as impressive. In Hordaland sea meadows such as this are rare small in size - they are more common in coastal environments.