Fisherman, I am a huge kayak guy. I would suggest a yak. I'm about your size and I have a Wilderness System 100. I use it for the same reasons, go way back in the shallows where boats can't go. I love my yak cuz I can turn on a dime and stay dry. Also, a yak is faster than a tube so if you want to cover a lot of water, yak. Of course, this is a yak, getting wet is obvious when launching, getting off, feet hanging off the side and the occasional swan drive to stay cool.
But seriously, a yak is dry from knees up. If you launch from a dock, completely dry. But, you need to try a yak and a tube. You need to find the right fit for you and your fishing style.
What yaks were you looking at?