In reply to Stevie989:
Don´t do it. Most inflatables handle like a rubber duck. They are high in the water and extremely wind sensitive and only good for rafting rivers with strong currents (for this they are excellent, no rigid elements that break when you bump into submerged rocks...).
Folding canoes or kayaks are much better, and can be found used at reasonable prices. They also hold for ages, so buying used is much less of a risk than with inflatables. Both canoes and modern kayaks fold to something like 40 cm by 120cm, so can easily be carried in public transport (older folding kayaks often have very long frame packs, 1.50m or longer).
For folding canoes I can recommend Pakboat and Ally, both make versions ranging from easily portable singles to expedition size doubles. Pouch make a beautiful folding canoe with a wooden frame, but I liked the previous model even better than the current one.
Recommending a folding kayak is harder, as there really are huge differences in weight, performance, and style. At the cheaper end you could look at aluminium framed Triton kayaks from Russia which are reliable and fast but not very nice, while at a bit higher price there are lots of excellent wooden framed models e.g. from Klepper, Pouch or Nortik (and other companies).
My favourite boats are made by the Canadian company Feathercraft and are again aluminium framed, but they are unfortunately out of my price range.
Still, a nice Feathercraft Khatsalano, maybe when the kids will have oved out....
CB