9 times out of 10, the reason my shotgun takes a swim is due to the fact I have unloaded it and have it leaning on a tree or the dog stand and I am watching the other hunters and kerplunk!
A sling is a good thing. Personally, they impede my swing and I do not use them but I do carry a floating case with a shoulder strap on it.
I think the point BigJim and others make and rightly so is to find what works for you. I hunt a lot with an 870----a lot-----but I think you are at a disadvantage due to the lack of a quick follow up shot and you tend to get off target when you jack the hull out at least I do anyway.