As part of the Southsea Coastal Scheme works, the rock will create new flood defences from Old Portsmouth to Eastney.
A barge and tug began delivering the material to shore yesterday.
The rock is being transported by the merchant vessel MV Liamare as well as a large barge, and then transferred to the Selina, an 84-metre long powered barge.
A Portsmouth International Port pilot will then manoeuvre the Selina from Spithead Anchorage A8 to Southsea seafront.
Rock will be delivered on a weekly basis until September, averaging 5,500 tonnes per week - with an approximated 137,00 tonnes expected to be delivered throughout the year.
It will be stockpiled in heaps from the beach adjacent to Blue Reef Aquarium.