It's no ordinary day at the beach. These divers are in Cornwall, southwest England, not for the fun but to pick up rubbish.
An estimated 70% of the plastic which enters the sea sinks, according to the organisation Dive Against Debris. And much of it is not biodegradable.
This is a problem that stretches far beyond the UK. Eight million tonnes of plastic ends up in the world's oceans every year, causing damage to this fragile ecosystem.