This is a very versatile kayak made by the Venture trademark of P&H Sea Kayaks of Great Britain. These are kind of difficult to find, but are well worth the effort.
This craft is just short enough to take it on some rivers (though nothing where you'd need to turn on a dime), yet long enough to track straight and fast on still water. Excellent secondary stability. Very comfortable seat (as far as kayak seats go). Ample room for a backpacking tent and a few supplies for overnighting. It has a fairly open cockpit, yet can still be fitted with a skirt for rougher conditions. I am 6' 4" and 190 lbs and this feels perfect and has adjustable foot pegs (can also be fitted with a rudder).
I've taken it on many Ozark rivers and it usually performs well, just not if you have to do a last second correction since it wants to keep tracking straight). This kayak paddles perfectly down the Missouri River or on any open water. If you will be doing only sea kayaking you might look at the longer 17+ foot long cousins made by P&H.