This morning i called 112 (the contact number noted on the swimming zones notice boards) and explained what happened to me yesterday.
The operator confirmed that only boats are not allowed to use swimming zones and that I could use my harpoon within a swimming zone. She then suggested that I contact the police depot to futher confirm this.
Called the police depot and the officer on duty also told me that using a harpoon in swimming zones is allowed, however he told me to contact the Qawra police station to double check

I called Qawra police station and spoke the officer there. They confirmed that I was right and that swimming zones are there only to restrict access to boats.
Before hanging up, the officer then told me that should I be passing by the Malta Tourism Authority offices I should go in and check with them if the area has been declared a 'restircted/protected area'......
I am now confused!