You need to plan yourself which way to come out here, surrounded by Marramarra National Park. As you drive up the river from Berowra Creek, you may encounter strong currents, particularly on outgoing tides and after heavy rain. The water is barely salty any more! The narrows between Friendly Bay and Big Bay may even show rapids. Subtropical rain forests to one side and Mangroves to the other. Take your time and have a rest to enjoy the splendor of the nature!
Big Bay Island lies in the center of the Big Bay, which, to one side, is covered by mangroves, and one may not even recognize it as an island. To the east, a fair part of the bay has open waters, navigable by a small motor boat at high tides. Landing is in the mangrove seam before you make your pleasant way up the solid land.
Be warned again of shallow waters, rocks and oyster farms, I have seen some of the poles fully submerged at high tide, so you better read the channel and drive carefully!