To be transparent, I was in Lisbon in February so there was no chance I'd be dipping into the Atlantic on this trip. However, I heard that Cascais was a beautiful town on the water, and I wanted to check it out. I just had to use my imagination and envision the beach filled with tanning Lisboetas in the warmer months.
The main tourist attraction in Cascias is called Boca do Inferno (Hell's Mouth), and to be honest, I wasn't that interested. Maybe if the tide were higher when we were there, it would have been more... scary? The name just didn't live up to what was, to be fair, a cool rock formation.
Oh, well. What the Boca do Inferno did do for us: it was about a mile down the coast from the Cascais train station, so it gave us a great excuse to have a nice walk and see the area. It was really pretty, and I bet in warmer weather, it would have been packed to the gills with tourists and locals alike. I definitely enjoyed seeing it and would recommend it for a half-day trip.