Sometimes the water you are in contact with can have bugs in it that may make you ill. These bugs can affect anyone’s health but some people may be more at risk, such as the very young, the elderly, or people with weak immune systems.
Natural Resources Wales and some local authorities regularly check for bugs at some bathing water sites from May to September. You can find the results of these checks online, along with further information about each site.
You may also come across algal blooms in water. Many types of algae can grow in huge numbers, especially in warm sunny weather, and form an algal bloom. Blooms may colour the water or form scum on the surface that may be smelly. There are many types of algae in the UK. These include blue-green algae (cyanobacteria) found in freshwater (e.g. lakes and streams) and marine (sea) algae which include seaweeds and tiny plants.
Whilst most blooms are not harmful, some can contain toxins which can cause itching, hay fever–like symptoms, nausea, and fever. As it is not possible to tell by looking at whether an algal bloom is harmful, it is best to avoid swimming where an algal bloom is present. Look out for signs along the water’s edge that may advise you not to use the water.
To report a bloom visit Natural Resources Wales or call their environmental incident hotline 0300 065 3000 (24 hours).
Other less common water quality hazards include Leptospirosis (Weil’s Disease) - an infection spread in the pee of infected animals; and swimmer's itch (cercarial dermatitis) - an itchy skin rash caused by an allergic reaction to tiny parasites released by infected snails. This is more common in the summer months.