scrub a dub dub a nuny in the tub

Nuny has out grown the baby bath. He was in it earlier this week and kept standing in it and slipping all over the place. So he is officially a real big boy bather!! But how do you tell an 8 month old not to stand in the bath tub!?! Even with the slip proof mat, he is still slipping and sliding and he hurt his little face because I was busy taking pictures to catch him when he fell. any idea's?? and dont say stop taking pictures when he is in the bath:)