In a manner related to or along the coast; in reference to coastal areas or coastal direction.
From coastal (relating to coasts, from coast + -al) plus -ly adverbial suffix. Coast derives from Old French 'coste' and Latin 'costa' (rib, side).
Coastally appears in geography and navigation texts—it's the way geographers precisely describe how something happens 'along the shore' rather than inland, which matters enormously for weather, ecology, and economics.
Complete word intelligence in one call. Free tier — 50 lookups/day.