They were left soaking in their seats when entertainer Marty Putz turned a water cannon on the judges panel.And Simon Cowell didn't need to mop up the mess on his own after he and fellow judge David Walliams, 46, were then covered in toilet paper on Thursday night's Britain's Got Talent  live semi-final.Finding the humour in the stunt while covered in paper, the music mogul, 58, admitted the childish act would probably appeal to his four-year-old son Eric.The chaotic comedic performance kicked off with a dizzying array of costumes and props, including a gigantic baseball mitt and marshmallow cannon.After drenching Simon, David, Amanda Holden and Alesha Dixon, with a water cannon, Marty then enlisted the help of host Declan Donnelly to carry a loo-roll propeller towards the panel.With Alesha and Amanda already annoyed by the soaking, the pair scuppered out of the way of the paper onslaught, leaving David and Simon to bare the brunt of the slapstick attack.Clearly taking too much enjoyment out of the hilarious skit, Dec flashed a beaming smile as he covered the music honcho in layers of paper Struggling to see out of the mess of loo roll on his face, Simon quipped: 'This isn't what I signed up for' as the paper wrapped around his head and cascaded down to the floor.Finding the humorous side, David reasoned: 'I'm a big kid at heart and I think the kids who watch the show will love it!' Meanwhile, Amanda, 47, was so angry about the surprise soaking that she stormed away from the panel along with Alesha, 39, with the girls taking cover and attempting to hide from the stream of water.Clearly still angry after his act came to an end, Amanda then stormed the stage to throw an entire bottle of water over Marty as he cowered away.The ladies then stood clutching towels and looking unimpressed by the act, revealing that they couldn't sit back down because their seats were wet.Clearly irritated by the soaking, Alesha remarked about the act: 'I had a good flush!' while Amanda gestured at her sodden gown, claiming 'I'm going to send you the dry cleaning bill!' Earlier in the night, Alesha and Amanda were looking slightly more glamorous as they competed to flash the most leg with their racy gowns.Ensuring all eyes would be on them as they made their way onto the stage, the stunning duo sashayed hand in hand sandwiched between Simon and David.Showcasing her sensational figure, Amanda donned an emerald green ballgown with a halterneck and a racy thigh high split.Offering a look at her tanned and toned pins, the blonde bombshell added to the glamour by boosting her petite frame with a pair of towering gold stilettos.Meanwhile, Alesha also looked phenomenal as she sizzled in a scanty gold mini dress that featured an ornate cape that skimmed over her incredible physique.