Hordes of Aucklanders are gearing up to hit the beach as summer approaches, but now there's a growing list of places to avoid.

Auckland Council has blacklisted 16 spots as unsafe for swimming, citing concerns over "long-term water quality".

The following spots are the ones to avoid:

Te Henga (Bethells) Lagoons

Piha Lagoon

North Piha Lagoon

Taumanu East

Green Bay

Clarks Beach

Tītīrangi Beach

Cox's Bay

Meola Reef

Weymouth Beach

Little Oneroa Lagoon

Wairau Outlet

Laingholm Beach

Wood Bay

Fosters Bay

Armour Bay

Signs were erected at the beginning of the year warning the water is not safe for swimming at the Piha and Bethells lagoons - both popular swimming spots.

Little Oneroa lagoon on Waiheke Island, Cox's Bay, Meola Reef and Milford Beach are also among those now with permanent signage.

More than 50 beaches are being closely monitored.

Newshub.