If your large tortoises are anything like ours the can tip up a water bowl the second they look at it!
These bowls have been tried and tested with our adult Sulcata, Yellowfoots, Redfoots and Leopards and none have managed to tip them up (a small miracle!)
70cm square, made of very strong plastic. Light enough to be moved around when needed and easy to clean. 
Plenty deep enough for them to have a good drink but also not high enough so they struggle to get in and out. 
Pictured with one of our leopards who is 13"