It's amazing. We were underway - at a slow speed (4 knots), really, but anyway propellers were spinning down in the water. He fearlessly approached ship's stern and climbed up. Spent some time on social visit, looking around with great interest and let us make some pictures.
I imagine what his mama told him when he returned home :)))
More seriously I suppose he was swimming in close proximity to the vessel, was dragged by water disturbancies to propellers and, struggling for life fiercely, managed to climb aboard.
Ht was launched safely into water after we stopped for a while.