We have had significant interference with very sad results. The appearance of black fins and white markings that circled us in smaller and smaller circles was positively identified as Great White Shark.  We had the shark shield in the water beside us but the shark was doing the classic "investigate whether the disturbance in the water was food". So we had to get onto the boat as the shark continued his search pattern in the area where Marilyn had just been swimming before finally turning and swimming away. So that was the end of the swim, just past halfway point after 8 hours of swimming and 8.5 nautical miles (15.6 km) from the start. We are all safe and heading back to marina with great disappointment.