One of the first decisions you need to make when purchasing a new kayak lies in the age-old argument of sit in vs sit on kayak. These are the two main types of kayaks.
Ultimately, the decision between the two is largely a personal one, but each type of kayak carries its own pros and cons.
If you know the differences between sit in and sit on kayaks, you will be better informed in your purchase, and you will likely be happier with whatever kayak you decide to buy.
Also read Canoe vs Kayak: http://www.gadgetreview.com/canoe-vs-kayak-differences