Thousands of sunseekers have descended on Brighton beach this weekend to cool off during some of the hottest temperatures we have experienced this year.

But tourists might be thinking twice about taking a dip after pools of brown sludge can be seen in the water, washing up on the beach. The picture above was taken today.

But what is it?

While many might be worried it could be another sewage outfall finding its way to the packed seafront, it is something which is, in fact, out of anyone's control.

The Argus: Brighton beach was packed with tourists todayBrighton beach was packed with tourists today (Image: Simon Dack)

Read more: 'It’s poo isn’t it?' - People spot brown lumps in sea

The smelly, greenish-brown scum on the surface of the water is a collection of algae which have increased in population rapidly.

In Sussex, this regularly happens in May as the weather gets hotter and residents have been reporting a lot of it in recent days.

The Environment Agency told The Argus: "It’s easy to mistake algae for sewage, particularly as both have an unpleasant smell, but foam on the water’s surface or on the beach is most likely to be the result of an algal bloom breaking down."