Opcina Marina, Croatia offers 12 beaches perfect for sunbathing, surfing, swimming, and more. Opcina Marina, Istria, Croatia, is known for its proximity to the Brijuni National Park and the historic town of Pula. The best time to travel to Opcina Marina, Croatia, is from June to September, with average air temperatures around 75°F (24°C) and water temperatures about 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!