Would be 10 says my daughter if she could put her head under. OUTSTANDING! The huge grins and screams of delight said it all. We had visited Waitomo, Hobbiton, Sky Tower and I was even visitor chief at Rotorua. This was better than the lot by some way, and they were good! The directions were just spot on. Warm, sandy/ gritty bottom so no worries re what’s under foot. Stayed in for 1 1/2 hours.