As long as it's dark enough to see into the water and will not cast a shadow, you ok. I make sure that the sun is not shining onto the spear hole or reflecting into it. I like mine as dark as possible, but it doesn't have to be totally dark. My uncles shack leaves alot to be desired by way of holes and letting light in. It is honeycombed w/ pinholes and has fist sized holes all over, yet he spears more pike than anyone I know. Just my $.02.