Natural Resources Wales is reassuring visitors to some North Wales beaches that bright orange-coloured water is not pollution.
It says it's a type of seasonal marine algae.
Officers have been testing the water at Penmaenmawr beach and have identified the early signs of an algal bloom.
There are reports Reports that the orange colour is visible at Llandudno and may also be present on other beaches in North Wales.
The Noctiluca marine algae, also known as Sea Sparkle, is common across the Welsh coastline during this time of year, and is a naturally occurring phenomenon.
The orange colour can be even more pronounced at night as it appears to glow in the dark.