Michel Roggo / Freshwater spring in the intertidal zone of the Piccaninnie Ponds Conservation Park, South Australia, Australia. March 2015 . Photographed for The Freshwater Project

Nick Upton / Common starfish (Asterias rubens) moving in a rockpool, real time, Cornwall, England, UK, September.

Nick Upton / Common prawns (Palaemon serratus) and a Rock goby (Gobius paganellus) feeding on a dead Montagu's crab (Xantho hydrophilus) in a rockpool, Cornwall, England, UK, September.

Nick Upton / Rock goby (Gobius paganellus) stealing food from a scavenging Common prawn (Palaemon serratus) in a rockpool, Cornwall, England, UK, September.

Alex Hyde / Various rockpool animals and seaweeds, photographed on a white background. Isle of Skye, Inner Hebrides, Scotland, UK, March. Digital composite.

Nick Upton / Split level view of a Beadlet anemone (Actinia equina) attached to a boulder encrusted with Maerl (Lithothamnion glaciale) a red coralline alga, in a large rockpool, Crail, Scotland, UK, July

Bertie Gregory / 2020VISION / Young boys playing, putting seaweed on their heads whilst rockpooling, Falmouth, Cornwall, England, UK, July 2011 Model released

Dan Burton / Young girl fishing in a tidepool on Exmouth Beach, Devon, UK, September 2009, Model released.

Dan Burton / Children checking their bucket for animals caught in a tidepool on Exmouth Beach, Devon, UK, September 2009, Model released.

Jose B. Ruiz / Aerial view of the Bay of Cadiz delta, Puerto de Santa Mara, Cdiz, Spain

Jose B. Ruiz / Aerial view of the Bay of Cadiz delta, San Fernando, Cdiz, Spain

Jose B. Ruiz / Aerial view of the Bay of Cadiz delta, Sancti Petri, Cdiz, Spain