March Wireless via eBay offers the LifeProof Nuud Waterproof Case for iPhone 6s Plus in Black, model no. 77-52574, for $34.99 with free shipping. That's a buck under our July mention and the lowest total price we could find for any color now by $11. It's purported to be fully submersible to 6.6 feet for up to one hour. This shock-proof case is also IP-68 rated for dirt and snow resistance.

Update: The price has increased to $38.