As an avid waterfowl guy that has about all the stuff needed to get to where ducks want to be, I have found a kayak is certainly a possible (and effective) vessel to hunt from, however, I have not found one that hunts well. There are trade offs to everything, But I found a 1236 jon boat customized to be a layout boat is much more comfortable. Dryer, more stable (however the right kayak can be just as stable), can put a motor on it if conditions warrant so, there are several factors as to why I sold my duck yak, and will be back in a small boat for skinny water/ sloughs. The biggest downfall of the yak for me was how to haul decoys, even a half dozen takes up valuable real estate, how to secure the shotgun so it does not get dropped in the water during transport or while hunting, and you are always wet. Even with waterproof gear on, the water is cold, and makes me cold faster. I am building a small jon with a deck from the middle seat forward to put a layout blind on and hunt from as I would if in a dry field. I can store decoys and a dry box full of extra ammo, gloves, etc. Plus have the benefit of running a small outboard, electric motor, or mud motor in the future. Sometimes too small is just too small. The only advantage of the yak I found was storage while not hunting, and it did not need a trailer. I could throw it in the truck, But when I got to the hunting spot in it, I was missing several of the things the made the day more enjoyable because there simply was not enough space to haul it all.
After all that, there are certainly A LOT of people that hunt from them and are very successful with them. I just never could find the right system to wok for me.
I would make a list of everything you MUST have with on a hunt, and see if you can come up with a way to keep in the yak and stay comfortable before you purchase one. The only good news is if you buy one, and it does not work out, they go fast on the used market. A $500 kayak on the used market brings $350 fast. There is going to be a lot more expensive things to cost you as a waterfowler that taking a $150 hit on a kayak.