Västerviks Museum and Södertörns Högskola/MARIS has an ongoing research project at Stäket, Valstad in Gamleby north of Västervik. This is a very exciting area with remnants from the younger Iron Age, including a facility consisting of hundreds of wooden piles in the narrow strait in the interior of gamlebyviken bay. There are several burial fields, hollow roads, a runestone and several farm locations from the time.
Ocean Discovery has assisted with 3D scanning from drones as well as examination with Side Scan Sonar. Ocean Discovery has also been filming the excavations since 2016 and the results can be seen in the video below.

https://www.facebook.com/vasterviksmuseum/videos/714075969373802