My partner and I are interested in purchasing a kayak. I did a bit when I was younger, but he has no experience at all. We decided that we want to get a tandem kayak.

Does anyone have any suggestions as to what to look for? We will be mainly using it in open waters (lakes, etc), and maybe some rivers, but no rapids or whatnot. They would mainly just be day tours.

May I suggest that you purchase a canoe instead? Kayaks are extremely unstable crafts versus a canoe. Plus you can pack stuff in the canoe that you can't in a kayak.

I had a dandy 16' fiberglass canoe when I lived in Florida and I went everywhere with it. I could put it on the top of my car with a few special rigid foam carriers and tie it down properly.

If your partner is not familiar with a kayak can you go somewhere and rent one for a day so they can see if they like it or not before you go ahead and buy one?

We will be renting for a bit, but he's pretty gung ho about it haha. After some discussion we've decided that it may be best for us to each get our own single kayaks.
I used to canoe when I was younger but I never liked it really, and preferred kayaking.

I don't need to worry too much about storage as we won't be going on very long treks.