So I park at a boat launch while at Harriman (Sebago) in NY state when I train up there. Everytime I say “I should get a kayak to cross train”
So, I turn to the collective wisdom of ST (which is all knowing) and ask.
“Which Kayak Should I Buy?”
consider
economics and recreational use…
MLT
i dunno what the water is like, but it probably depends on the kind of kayaking you’re going to do. There are lots of good, cheap recreational kayaks, and the sit-on-tops can be cool. Spend more and get a longer sea or a shorter whitewater. Personally, I love whitewater, finding a spot to surf, roll, etc. What kind of paddlin’ were you looking to do?
There is a good summary here ;
http://www.rapidascent.com.au/PDF/KayakTestingArticle.pdf
Not sure how relevant it is to the USA. There is a heap of triathletes paddling here for the new sprint adventure series. We are all disasters in the water, but getting better.
I love my Perception kayak. Love it love it love it. IMO, in your shoes I would get a sit in type of kayak built for touring or day tripping. The longer hull and the possibility of a rudder means it is easier to go in straight lines and you can spend more time just paddling and getting a good, rythmic workout in and less time navigating. Also, the fore and aft hatches (if yours is so equiped) are great to put gear in if you ever want to bring stuff with you or go on a multi day camping\kayaking trip. Those are tons of fun.
Mostly lake paddling. For whitewater trips I’d probably rent from a local…same for ocean.
Something simple…Much like tri-bikes the possibilities are endless and confusing…
thanks,
MLT
I had a Dagger Zydeco - entry level recreational kayak. Loved it. I used to take it out to the lake with some sandwiches and books, and eat/read/nap in it 
It even had room for me to take my dog and he’d sit in between my legs. It’s just a regular kayak, and there are very many like it (Perception swifty is another good one)
From my experience, you’ve mainly got 3 kayaks.
Sea - long ones, great trackers, fast, but pretty big and narrow, and they’re not as agile
Recreational - great all around, but aren’t as fast and don’t track as well as sea
Whitewater - well, pretty much for whitewater only Usually somewhat uncomfortable, don’t track for shit, but can do 720’s on a dime.
Then you’ve got sit-on-tops, which are like uber recreational. Those are cool for just tooling around, but I dont know much about them.
If kayaking were good for cross training for Tri, then I wouldn’t be such a crap swimmer, now would I? :-p
I can paddle like a madman, I’ve been doing it for years and I’m pretty good at it. There apparently is nearly zero carryover to swimming (and certainly less than zero for running or biking). It’s a fun sport, but do it for its own merits (of which there are many), not cuz ya think it’ll help ya SBR any better.
A great beginner boat is the Perception Acadia. We started with these, they are short sea kayaks (I think 11’?), recreational use intended. A notch up from this would be something like the Carolina, which is a bit longer, and therefore faster. Another comparable one is the Necky Looksha Sport, these boats are about 14’ long or so.
Now we have full-on sea kayaks, my wife’s is a Perception Shadow (16.5’), mine is a Necky Looksha 4 (17’ - and they now have finally come out w/ the Looksha 5, which looks(sha) pretty sweet 
Yer from Joisey, so if yer gonna buy, go down to the Jersey Paddler, down in Brick. It’s worth the trip, you can demo boats in the nearby pond, and find out what you actually like, rather than what sounds like you’d like it from the marketing materials. You’d be surprised at the differences between how boats actually paddle, and if yer gonna be spending upwards of a $K or more on one, make sure you get what you want.
Perception is kinda like the Trek, Cervelo, and Cannondale of kayaks, all rolled into one.