By the Sea — No. 4

Across

1. A large brown seaweed (4)

4. A moving swell on the surface of water (4)

6. A heavy object used to hold a boat in place (6)

8. A bird commonly seen near the sea (4)

9. A sea creature with claws (4)

10. A hard covering you might find on the beach (5)

11. The tall pole supporting a boat's sail (4)

12. The regular rise and fall of sea level (4)

Down

2. A structure extending over the water from shore (4)

3. A smooth gem sometimes formed inside an oyster (5)

5. Land along the edge of the sea (5)

7. The star that warms a day at the beach (3)

9. A shellfish with two hinged shells (4)

10. Tiny grains found on a beach (4)