I know the ACR has a 15 foot depth rating but a lot of guys like to carry them diving as well in case the boat leaves you and the divers I run with vary depth from 150 to 300 feet underwater. If I got hit by a 100 foot rogue wave on a boat and by some miracle survived it, I would want to make sure my gear could handle more deeper water.
Also I will admit Doug, Watershed could do allot better on there presentation and use of there product and it's to bad they never took your recommendations but what can you do. Their web site doesn't give there product any kinda promotion whatsoever. If it wasn't for me trying one of there products out for experimentation, I would have never bought anything. I was so impressed with there products, I purchased all of there deck bags, all but one of there duffel bags and 1 backpack because they performed outstanding for the use I put them through. It was only when I got my bag when the warranty (lifetime) and depth rating (200-300 ft) was given. These bags have been so durable that all my electronic gear and sleeping bags and other critical stuff goes in them. I put all these bags in Osprey or north face packs depending on where I'm going and I can use them as a PFD (personal flotation device) if needed.
It was nice when I traveled overseas to have all my belongings carried on the boat taken with me while diving and not have to worry about boat handlers going through your stuff while underwater.
Example of grab bag: (2 watershed bags in a North face back pack)
Inside the bags 40 watt Solar cell and chargers,cables, GPS, Steripen, VHF radio, Combi filter, OR micronight Bivi, fire equipment, first aid kit, signaling equipment, compass and misc other things for example. Bags are rated at 200 feet underwater and the back pack is positive buoyant and can be used as a flotation device. Also I carried this backpack as a carry on overseas and even on puddle jumpers and had no problem with overhead bin storage or anybody giving me a hard time with the size.
Sure Shot Backpack from The North Face
http://www.mountaingear.com/pages/product/product.asp/item/211667/N/0/cmpn/900000/CMP/KNC-900000