You are allowed to fish where you can get down to the water, but of course you can not go into people's gardens and private areas. It is allowed to use up to 2 rods.
It is allowed to use belly boat. However, you must respect the Regulatory for the Vandkraftsøen, which has been prepared by the municipality of Holstebro. Map of the sailing area can be found here. You can read more about the sailing rules for Vandkraftsøen here.
Detailed map of Vandkraftsøen: