Humidity Advice For Water Snakes?

[annarawrr]

Hi guys,
I just received my first snake from a breeder a few days ago. He's a young plumbeous water snake and sadly there is not much information online about keeping these snakes as pets. He's a few months old and seems healthy, he ate two small fish on his second day home and comes out briefly every night for a drink and lap or two around the tank. I've kept handling to a bare minimum. Overall he seems fine.

However, I'm not really sure about the humidity levels required. I'm using a coco peat substrate recommended by and received from his breeder and I was told to keep it damp. Alternatively I read online (not for plumbeous snakes per se, but generally for water snakes) to keep a dry substrate because too wet could cause water blisters. So what's the verdict? Anyone have any information that could help? (: