After a couple more hours of swimming around, hanging out with each other, and being mermaids, Aziraphale and Crowley decided it was time to head back home.

They left the water, and somewhat solemnly miracled themselves back into their usual forms. They put their clothes back on and climbed into the Bentley. 

Once they arrived at Aziraphale's bookshop (since they both decided they would crash there for the night), they flopped onto Aziraphale's bed and fell asleep immediately. They dreamt of dolphins, mermaids, and each other.

The End.