There is a very cool old tram in Porto that runs along the Duoro River edge. For 2.50€ you can take the tram all the way out to the edge of Porto, where the Duoro River meets the Atlantic Ocean. There aren't a lot of beaches, but there are plenty of long walkways that stretch out into the ocean, which make for spectacular views.

I snuck a pic of Walk when he wasn't looking.

Another lighthouse, clearly ready for its close-up