Okay, it looks like he took some water in the lungs. Bubbles in his mouth is not good. I've seen this before, and he's having trouble breathing. Either there's an obstruction or water got into his lungs, or both. Try to put him butt raised and at an angle and lightly tap his top shell, left aide and right side. See if bubbles come out.
Okay, you put him to sleep. Please check on him during the night. If you see bubbles coming out of his mouth, do what I just suggested. Hopefully, this will help relieve the symptoms. Then, in the morning, take him in and tell the vet all that was done.