The Mill Pond in Pembroke
A very fine statue of Henry VII keeps sentinel at the Mill Pond over Pembroke Castle.
This total length of the path alongside the Mill Pond is about 600m. You can choose to walk no further than 20m and watch the swans. Alternatively you can go right to the end of the Mill Pond, take the path to the right up to Pembroke Main Street, and then walk back through the town.
The car park outside the Royal George costs 50p for an hour; and from here you can use the zebra crossing to reach the footpath.
It is also possible to both visit and walk around the castle itself from here.
Incidentally, the water around the castle is no longer tidal. A barrage has been built not only to keep water around the castle but also to hold back high tides, and reduce flooding on the Commons car park. If you walk down and stand on the barrage you'll see wading birds in the tidal mudflats to the west.