海岸に

to the coast; at the coast

→ 海岸
phrase Uncommon #14,831
to the coast; at the coast 海岸 means “coast” or “seashore,” and に marks a destination or location. The exact translation depends on the verb.
JA: 夏休みに海岸に行きたい。
EN: I want to go to the coast during summer vacation.

どうやって海岸に行けばいいですか

How do I get to the beach?

このバスは海岸に行きますか

Does this bus go to the beach?

ねえ海岸に行かない

Hey, want to go to the beach?

— 魔女の宅急便 (1989)

海岸にたくさんがいます

There are many turtles on the beach.

海が海岸に入り込んだ

The sea encroached on the coast.

海岸には大勢の人がいた

There were a lot of people on the beach.