Aziraphale waits patiently for ten minutes while Crowley figures out if it's safe or not, and when he gives the go-ahead, Aziraphale shrugs the robe off of himself and then places his towel on the bench as he steps forward less than one inch at a time to find the edge of the pool.

He is probably going to need some assistance.

Eventually, he does dip a toe into warm water, and he bends down to lower himself in, as he has no idea how deep it is or how slippery the bottom.

When seated, he does feel a sense of calm, and he reaches out for Crowley.