I have the 2 person Diveyak (not the newer XK2020 thing). I don't know where you'd fit 4 tanks on it, or how you'd go about swapping tanks, but two complete kits fit on it just fine. It looks something like this rigged out.
http://www.deep-six.com/page92.htm
When I was using it, I'd carry it down to the water, then strap everything to it, then paddle away. I carried a small folding anchor, stowed in a bag in one of the seatback pouches, and just clipped it to one of the d-rings when we got to the dive site. I have two clip lines (6ft long with bolt snaps) to clip the BC's to and prevent from sinking/floating away, then kit up in the water. Getting on is the reverse. Clip your BC, then get on the kayak and pull your gear up and strap it back down. It does store easily in the garage or a closet, but the stock paddles and pump are barely adequate. I bought some real Ocean paddles with leashes and a double action hand pump. After that it worked very good and I could set up the whole thing in about 5 minutes.
It's rock solid when on the water (not tippy feeling at all), but blows around in the wind if you don't put the skegs on. I never tried to launch in heavy surf, but in light/moderate stuff it wasn't too bad. Also, make sure that you cinch the seats up really tight (to the point of the back being forward at the top), otherwise you'll slide down, making your back sore.
Now I mostly dive from my Avon inflatable. But obviously that's more money and more hassle (engine, gas tanks, registration, etc.), but I wouldn't hesitate taking the kayak out.
http://www.deep-six.com/page92.htm
When I was using it, I'd carry it down to the water, then strap everything to it, then paddle away. I carried a small folding anchor, stowed in a bag in one of the seatback pouches, and just clipped it to one of the d-rings when we got to the dive site. I have two clip lines (6ft long with bolt snaps) to clip the BC's to and prevent from sinking/floating away, then kit up in the water. Getting on is the reverse. Clip your BC, then get on the kayak and pull your gear up and strap it back down. It does store easily in the garage or a closet, but the stock paddles and pump are barely adequate. I bought some real Ocean paddles with leashes and a double action hand pump. After that it worked very good and I could set up the whole thing in about 5 minutes.
It's rock solid when on the water (not tippy feeling at all), but blows around in the wind if you don't put the skegs on. I never tried to launch in heavy surf, but in light/moderate stuff it wasn't too bad. Also, make sure that you cinch the seats up really tight (to the point of the back being forward at the top), otherwise you'll slide down, making your back sore.
Now I mostly dive from my Avon inflatable. But obviously that's more money and more hassle (engine, gas tanks, registration, etc.), but I wouldn't hesitate taking the kayak out.