You point out there's a fairly obvious solution to the problem of the microphone not working: you don't need a microphone in the ocean. They’re whales. They can just sing the songs themselves. At first the whales are quite shy about the prospect (they don't often sing for an audience they can see), but after some coaxing you convince a particularly social Humpback to sing a few songs for the party. Soon, the others join in with surprisingly poignant and complex harmonies, and the sound of giant whales singing a cappella resonates through your camp and beyond. As the night proceeds, a large crowd has come to check out the whale chorus, a great atmosphere forms, and the good times go long into the night.