Cryptic crossword No 4,057

Across

1. Carbon fibre surf essential or another name for the coast? (8)
2. Sudden gust that can send a seaman flying (6)
3. In the countryside, far from the harbour crowd (5)
4. Frothy wave crests - or mountain peaks? (9)
5. Brand always good for a brew (9)
6. Sweltering, as the sand at midday (2,3)
7. Peak occurring twice daily at the coast (4,4)
8. Spotted swimmer that glides like a bird beneath the surface (5,3)
9. Shannon surf town, where lake meets river (8)
10. See 15
11. Energy one needs to lift the sail (5)
12. Search the shore for treasures washed up... (9)
13. ... such as this, useful for the bonfire (9)
14. Can be deep, flat, forward or back - affecting how the sail prevails (5)
15. Like a tune that sticks, or a wave that's just right for surfing (6)
16. Rollers as they crash and land (8)

Down

1. Sandy ridge, to leave a boat high and dry? (6)
2. Apero time across the Channel (4-5)
3. Tanker, technician or sailing garment (5)
4. Sore, deep, intense or unprocessed, as sashimi... (3)
5. Most seasick on a rough crossing! (9)
6. Flooded by the waves (5)
7. Be beaten by, as a sailor to the storm (4,2)
8. Something to toast a day at sea (4)
9. Ocean surge or billow (5)
10. Simple knot to secure the sheets (4,5)
11. Atlantic-crossing activist (5)
12. Medium for recording whale song, or an 80's mix! (9)
13. Of the chilly north, like seafaring Vikings (6)
14. Dies down, as a storm at sea might (6)
15. Slightly wet, like sea spray on the face (5)
16. Floating marker bobbing in the bay (4)
17. Tiny freshwater creature, or many-headed mythical water beast (5)
18. Tanzanian coastal haven of peace (3)