Juma Muita is a rugged seafarer, a burly Tanzanian who has navigated commercial vessels through some of the world’s roughest waterways. But mention one particular stretch of ocean to him, and his tough demeanor quickly gives way to something resembling fear. “I’m used to the life at sea,” Mr. Muita said from the bridge of the Semlow, a 187-foot cargo ship, as it was undergoing repairs recently farther down the Indian Ocean coast from here, in Mombasa, Kenya. “I’ve been everywhere, and I’ll continue to go everywhere, just not anywhere near Somalia.” Full Story