The Portuguese Coast Guard has advice for boaters who find themselves among orcas: Cut the engine, lock the steering and hope they get bored.
The advice came after the National Maritime Authority sent crews out to rescue two people aboard a sailboat about seven kilometers off the coast near São Julião. The past year has seen increasing numbers of reports of orcas harassing or playing with (your point of view) small craft. The sailboat was towed to a marina in Cascais "for safety reasons for navigation."
Official advice from the Maritime Authority, jointly with Institute for Conservation of Nature and Forests: "to all mariners that, in the event of sighting of these mammals, the engine be turned off, in order to inhibit the rotation of the propeller, and immobilise the steering wheel, thus discouraging these mammals to interact with the mobile structures of the vessels.”
In other words, sit tight and hope they get bored and go away.