What began as rare encounters off the Iberian coast now shows up in captain’s logs from Galicia to the Strait of Gibraltar, and in wary chatter on VHF. Experts say it looks learned, even coordinated. Insurers are watching. Mariners are changing habits mid-season. It started like a shiver through the deck plates. A coastal freighter off Cape Finisterre rolled on a glassy swell, the night bridge lit soft blue, an ordinary watch with the engine ticking steady, when the helm shuddered as if from a hidden hand. The bow kept true, but the autopilot clicked off and the rudder felt...