Question from a prospective newb

[Streak]

Hi all,
I have lived inland all my life and recently moved to the coast.
I have been loving the fly fishing here both off the beach and in the SD bay.

My float tube has seen better days and its time to get something new. I figured why not look at all of the options including a kayak which is what brought me here.

For me, the pros of the tube are comfort, hands free to fish while the legs do the work, portability, easy storage etc.
The main con is not being able to travel great distances due to the drag of the tube and often battling against wind and current. Despite this I have been very fortunate in the places I have fished and have caught hundreds of fish in the 7 months I have been fishing here.

I have always dreamed about one day owning a fishing kayak and heading out to sea. However I really do get sea sick. I borrowed a friends kayak, launched from Fletcher's cove and did a couple of miles towards LJ. I really started feeling ill and had to beach in a hurry!!

So, if I were to get a kayak its only use would be to fish in the bay.
My sessions in the tube last 3 to 4 hours (held to ransom by my bladder!).
I am also concerned about lower back pain with ones legs stretched forward for so long. I am 6'1" 210lbs and at 52 my body is not as supple as it once was!

Given the above would I still be a candidate for a kayak (inflatable or rigid) and if so what kind?

I will be fishing the bay on Thursday in a kayak as a guest of someone who is using a guide service after which I will have a better idea.

Thanks in advance!