Crveni Otok, Croatia offers 1 beach perfect for sunbathing, surfing, swimming, and more. Crveni Otok, Istria, Croatia, is known for its picturesque St. Andrew's Island and the historic St. Andrew's Monastery. The best time to travel to Crveni Otok, Croatia, is from June to September, when the average air temperature is around 75°F (24°C) and the water temperature is approximately 73°F (23°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!