I wanted to know if its possible to do horror from the deep without having any prayer.
Is it a matter of food, recoils are hitting the monster for it's weaknesses?

I did it without prayer back on Zaicoranger. All you need is a bunch of food and runes(Bow and arrows if you want to speed it up, easier without IMO).

There is a safespot down there where the monsters can't hit you, but you can't hit them either, it's nice if you feel like you are about to die and need to eat though.

It isn't really any hard. I guess wearing a recoil ring will help.