Old Man Bay, Cayman Islands offers 4 beaches perfect for sunbathing, surfing, swimming, and more. Old Man Bay, North Side, Cayman Islands, is known for its proximity to the Queen Elizabeth II Botanic Park and the Crystal Caves. The best time to travel to Old Man Bay, Cayman Islands, is between March and June, when the average air temperature is around 82°F (28°C) and the water temperature is approximately 80°F (27°C). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!