Mike Davies photographed this amazing spider in 2009 on the Tennant Canal at Pant y Sais Fen - an SSSI not far from Neath.
These amazing spiders reach around 5cm in length when fully grown but are completely harmless and extremely rare so don't panic.
To put it into context - up until a few years ago, this species was only found in two locations in the whole of Britain and they were both in eastern England.
It is one of Europe's largest and rarest spiders and protected under the Wildlife and Countryside Act 1981.
We're very lucky to have them in Wales and the population seems to be thriving. The spider feeds on small fish such as sticklebacks and tadpoles and other aquatic invertebrates.
When the prey is located the spiders can actually run across the surface of the water to attack and can even hunt underwater by running up and down reeds!
Watch a clip about this remarkable arachnid from Iolo's Welsh Safari: