If you’re visiting Muir Beach and want to stop for a nice warm lunch after some chilly beach time, try the Pelican Inn, which is right there — Christa recommended it, and I approve greatly. They seem a little understaffed right now (like everyone), so be prepared for a wait and some chaos.
But the food is tasty, the beverages ditto, and the ambiance is pure Britain. A lot of fun. 
If the weather is nice enough, you can eat & drink outside too. Do bring proof of vaccination with you; they request it.
