You have to make up your mind whether you want a kayak for water travel or one that fits in your closet. Short waterline boats are very inefficient. That means that you, as the motor that drives the thing, will have to work harder to go a given distance. And if you are with others in longer boats you will have to hussle to keep up.
I was at the Cincinnati Paddlefest two week ago and there were about 600 plastic kayaks making the 8 mi. float. The standard size seemed to be about 11 to 12 feet. Personally, I wouldn't acquire a paddleboat less than 14 feet but most folks seem satified with the 11-12 class.

: I'm looking to pick up a cheap ocean kayak for some really basic
: river floating. Got the yak in mind, an 8 ft. Calypso
: (http://www.amazon.com/Lifetime-Calypso-Kayak-Blue-8-Feet/dp/B0045YO3UU/ref=sr_1_1?ie=UTF8&qid=1310163921&sr=8-1).
: My issue is transporting it on my '97 Civic EX coupe
: (http://images01.olx.com/ui/1/67/23/3486423_1.jpg). I'm looking
: at this Sherpak Universal Roof Rack kit
: (http://www.amazon.com/Sherpak-Universal-No-Skid-Kayak-inch/dp/B000YXI4K6/ref=wl_it_dp_o?ie=UTF8&coliid=I16FESPFWB553U&colid=115T81I9X5OOU)
: and wondering if it'll be sufficient for mounting the kayak to
: my car. Thoughts? Suggestions?