The inner area near the Quarantine Station is particularly good for common sea dragons and the rarer red indianfish. The reef on either side of Nielsen Park is worth one or two dives, but it is not of the highest quality. Divers and snorkellers should note that spear guns and sling spears are classed as prohibited weapons in national parks. Carrying these through the park is illegal. There's good fishing from the park's rocky shorelines and sandy beaches.
Fish are numerous - particularly flathead, tailor, snapper, mullet, bream and jewfish.
Popular fishing spots can be found near Nielsen Park - along the Hermitage Foreshore Track or on Bottle and Glass Point. If you're going fishing in the park, please be careful not to leave fishing tackle behind - wildlife can be harmed by it. Please note that netting and spear fishing are not permitted in the park, and it is forbidden to collect crustaceans and marine animals from the rocks. You'll need a licence to fish anywhere in NSW, including in the park's waters. Licences are available from the NSW Fisheries website.