Whilst the ferry, Proclaim, hove to, Dr Poore discussed with us some of the underwater life around the very popular (in season, of course) swimming beach, Neilsen Park, which is on the southern shore of the harbour. Much of the harbour foreshore is national park.
Neilsen Park is one of a number of harbour beaches that has a shark net.
This net has encouraged a growth in the population of a tiny variety of seahorse which uses the netting as a breeding ground. So many seahorse cling to it, that it gets too heavy to do its job properly and each off-season, is 'cleaned' by National Park rangers and UNSW researchers. Sydney Harbour is home to two species, the potbelly seahorse and the more common White's seahorse.
Just in front of the sandstone rocks, is an underwater 'field' of seaweed which has been infested by the Long-Spined Sea-urchin which breeds in warmer waters. Because the Eastern Australian Current is 2 degrees warmer over the last decade, this urchin has now spread as far south as Tasmania with disastrous effects on the more jungle like seaweed in those waters.