The water was clear. We saw fantails, a white-faced heron, cockatoos, ducks and a few fish. No jellyfish. On the shore of the island were tiny sandy beaches framed with palm trees.
After our kayak ride, we walked over the hump of land where Narrabeen's houses are, and had our first proper view of the sea, with rolling breakers and miles of sand, morning glory and yellow sea flowers (climbing guinea flowers?) growing in the dunes. There were no shops or lifeguard stations here, so this beach was fairly deserted. I don't know whether or not it would have been safe to swim here.
For lunch we discovered a really good South Indian curry place on the main road, that opened just for us, when they saw us coming.