Castlerock, United Kingdom offers 3 beaches perfect for sunbathing, surfing, swimming, and more. Castlerock is known for its stunning coastal scenery and proximity to the Mussenden Temple and Downhill Demesne. The best time to travel to Castlerock, United Kingdom, is from June to August, when the average air temperature is around 15-20°C (59-68°F) and the water temperature is approximately 14-16°C (57-61°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!