I was impressed, because I was expecting remnants of stone fishing weirs, but this is much more interesting:
Divers Arne Sjöström, Beesham Soogrim and Krister Kam Tayanin inspecting a 8000-9000 years old fish trap in the detritus mud (trap no 2). The trap has been exposed due to wave actions and erosion by sand and stones. The exposed part of the trap is c. 0,5 x 4 meters. It is made of long hazel (Corylus avellana) sticks. A similar trap in the area has been radiocarbon dated by Jan Öijeberg (Malmö Museum) to c. 9000 years before present (calibrated) (fish trap no 1) . There are no visible signs of bindings between the sticks but any strings should have been eroded away at the exposed part of the trap. It was used for fishing in the damed Verke river valley during the mesolithic, before the area was flooded by the sea.Recently exposed by wave action, just as wooden implements are being exposed by melting glaciers - and probably ephemeral once wood-boring worms find it. Very cool find.
The video could benefit from tighter editing; suggest skip to 1:05 to begin.