A GRANDSON of the Wild Oats XI owner Bob Oatley has been charged after an alleged assault on an elderly penguin warden who was trying to prevent a dog attack at Manly Cove on Saturday night - only weeks after seven penguins were killed by a dog in the area.

James Oatley, 27, of Mosman, was allegedly among a group of people on a boat that was pulling into the beach about 9pm. It is alleged he jumped off the boat and was followed by a large, short-haired dog believed to belong to the boat's skipper.

Only trying to help ... Angelika Treichler near Manly Wharf, where she protects the remaining penguin colony. Credit:Steven Siewert

As soon as the dog was on the beach it started running towards a female penguin that was making its way to its mate, which was nesting further up the beach.

Angelika Treichler was guarding the penguin with a fellow penguin warden, Johnyth Burton. ''I put myself between the penguin and the dog,'' she said. ''I was running up and down the beach and the dog was trying to get past me.''