Maybe it's the angle of the picture, but it looks to me like a careless turtle could fall out of the box and miss the tank entirely over on the left side (left from my point of view - the side of the box that the ramp DOESN'T go up.) Are you pretty confident this couldn't happen?
There is actually a small piece of wood that prevents that, I've watched them try and its funny, they make a little splish when they fall into the water. They also try from the ramp to the tank edge with the same result.
And here is some more love:
A Beagle/Basset
3 Cats
2 Red Eared Sliders
A Bunch of Fish
Whew, what a place