Beyond Güemes, the air already smells of salt. Then you reach the fork, and it decides your day.
The inland route takes you straight to Santander. Calm and no-nonsense. Many pilgrims choose the coast: over the cliffs to Somo, with the sea beside you and a wide view. In Somo you board the ferry across the bay. That way you arrive in Santander over the water, a lovely entrance after days on land.
It’s an easy day with little ascent or descent, about 5 hours of walking. It can get properly windy on the cliffs. That leaves you time for Santander itself. Check the ferry times beforehand, so you don’t end up standing on the quay in Somo for no reason.