The inlet is a wave dominated estuary with a high sediment trapping efficiency, it is always open to the ocean and the water is turbid. The total surface area of the inlet is 20 square kilometres (8 sq mi).
Hardy Inlet is the wide, lower basin of the Blackwood Estuary with a long narrow and shifting entrance channel. The majority of the inlet is made up of shallow banks with a depth of less than 1 metre (3 ft) found between channels between 2 metres (7 ft) to 8 metres (26 ft) in depth.
Algal blooms have been recorded in the inlet around Molloy Island and West Bay as a result of elevated nutrient levels, particularly Nitrogen and Phosphorus levels. Warnings have been issued so that people do not consume shellfish such as mussels and oysters which can filter out the toxic algae.
Commercial fishing was once conducted within the inlet but all licences have now been cancelled and only recreational fishing is permitted.
- "Estuary Assessment Framework for Non-Pristine estuaries - Estuary 649 - Hardy Inlet". 2000. Archived from the original on 23 May 2009. Retrieved 4 March 2009. CS1 maint: discouraged parameter (link)
- "Notice to Mariners - Hardy Inlet". 2007. Retrieved 4 March 2009. CS1 maint: discouraged parameter (link)
- "Department of Environment - Park Finder - Proposed Ngari Capes Marine Park". 2008. Retrieved 15 October 2010. CS1 maint: discouraged parameter (link)
- "Algal bloom in Hardy Inlet and Blackwood River region". 2008. Retrieved 4 March 2009. CS1 maint: discouraged parameter (link)
- "South West Catchment Council" (PDF). 2008. Archived from the original (PDF) on 23 July 2008. Retrieved 4 March 2009. CS1 maint: discouraged parameter (link)