Susami, Japan offers 8 beaches perfect for sunbathing, surfing, swimming, and more. Susami is known for its unique Underwater Mailbox, a popular attraction for divers. The best time to travel to Susami, Japan, is from April to June, with average air temperatures around 15-25°C (59-77°F) and water temperatures ranging from 18-22°C (64-72°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!