Is it okay to leave cooked octopus in water till next morning? I've cooked octopus in a boiling water (well, more like in own juice to be more precise) like I usually do and than I've realized that I'm too tired and going to eat it tomorrow morning. My question is: what would be the better option - to take it out of water or to keep it there? 

I don't now what happens with cooked octopus left in a water for about 8-10 hours. 

Just to clarify - it's question about keeping it in water and not about room temp. In my experience nothing happens with a hot pot slowly boiling down till morning - however I am actually going to put it to refrigerator after all.
I've realized that the price of mistake is not the high anyways so I've just divided cooked octopus to two parts: one left in water, another one not. This morning I finally have an answer!

It's better to take cooked octopus out of water but it won't be a tragedy if you didn't.

While both meals were tasty, octopus left in water was slightly slimy - it was a very subtle difference however noticeable.