Disco 1 Power steering and puddles.

If I drive through any sort of puddle, I lose power steering for a few seconds. It's like the belt gets wet and slips, but I've had a good look and can't see where water is getting to any of the pulleys. Has anyone else had this? I'm thinking worn belt or tensioner, hopefully the belt!

Is this a new problem?

Cheers

Relatively new. Been like it for about 6 months, lol