The mouth of the harbour is quite narrow, making for a fairly strong but manageable current on the spring ebb tide. We had to watch out for passing boats as it's a busy shipping entrance.
The U-Boat pens are used by local nautical industries, although one looked occupied by Naval types.
Nobody challenged us as we paddled around outside, although we knew we weren't allowed to paddle inside. This isn't a problem as we had a great view and could paddle around for as long as we liked. The sheer scale of the place is impressive and it is easy to imagine the place in use during wartime.
Outside the pens are some boats that I presume were scuttled to prevent the pens from being used...