Something that I'm often asked about is kayaks for kids. My goal here is not so much to provide an answer (there is no one answer), but to give my opinion and to give you some things to consider. Before I begin, here's a bit of a caveat:
- Before sending your kids off into the great big watery world of paddling set some rules for them and you to live by.
- Paddle with your kids.
- Consider the conditions: water temperature, wind, weather, boat traffic, currents, and more, and be prepared for those conditions to change.
- Keep them close. A kayak can easily move a kid out of a safe range. Winds can easily start pushing them away from safety. Winds often are stronger away from shore.
- Learn some rescue & recovery skills, and practice them!
- Learn to tow.
- Don't be afraid to play around and have fun. Getting wet can be a fun way to get in some great rescue practice.
- Adhere to the principles of PaddleSmart.
Finding kayaks that fit kids is a challenge. The most common approach that I see is that people buy the shortest kayak that they can find - usually also the cheapest kayak that they can find (typically department store kayaks). The problem with going short in a kayak not designed for kids is that the kayaks are very deep and very wide. These kayaks are meant to keep a 300lb adult afloat. I am no fan of these short, wide poorly designed kayaks (that also lack safety features like bulkheads and perimeter lines) for adults, and it's worse for the kids. Compared to an adult, a kid or teenager has a short torso, short arms, and light weight. The shorter arms and torso mean that they are unable to reach the water with a paddle in a natural and efficient manner. Further, the child's light weight mean that they don't immerse these kayaks to their designed depth and so they float a bit like a leaf on the water. All of this makes them hard to control the direction of, allows them to be easily pushed around by the wind, and generally inefficient to paddle what is already an inefficiently designed kayak. Having said that, these craft can make OK beach toys - paddlecraft that are paddled wading-distance from a swimming beach in very protected waters and calm conditions.
The trouble is that there are few options that fit kids well, and the options that are out there can be hard to find and somewhat expensive. But, there are options. There are a couple of kid-sized kayaks on the market. My kids paddled a Wilderness Systems Tsunami SP (SP = small person), a 12' fully featured sea kayak scaled to fit a kid. I find it tends to fit kids up until about 12 years of age. Another option that will last longer as your kids grow is kayak designed to fit women or smaller-framed adults. As your kids grow though their teenage years, they will quickly be filling in these kayaks and soon be making a great connection with the kayak. Still another option for those with a bit of time and that don't mind tackling a project is a home-built kayak. There are some fantastic kits and plans out there and often these can be scaled to fit the paddler. There is a company in BC that is making a kids kayak (the Squid) as a kit which I've seen in person and it looks just fantastic, would be easy to build, very strong, and light weight. http://www.madekayaks.com/kits/
I have also built a kayak for my kids using the methods and plans shown here: http://www.yostwerks.org There are some great designs, are relatively easy to build over a few weekends, and pretty low cost (I think my little Sea Flea, pictured below, cost about $120 to build using good cedar). These skin-on-frame kayaks are lightweight and way tougher than you might think.
I believe that fitting a kayak is really important for paddlers to have a great experience, for adults and kids alike. I believe that fit is more important than factors such as length, depth and width. By fitting the kayak well we are able to connect with the kayak at our bum, feet, knees/thighs, hips and lower back. These points of connection improve our control of the kayak and help us feel much more stable in the kayak. Poor fit can often be improved with pieces of a closed-cell foam (won't absorb water) glued into place. Extra padding added at the hips and knees can really help us fit our kayaks. As for length, a longer kayak moves more easily through the water than a shorter kayak, and it holds a straight line better. Conversely, a wide kayak moves more slowly through the water. This is another place where the short/wide kayaks don't serve kids well since they are still developing their strength and the short/wide kayaks are the hardest to move forward through the water and the hardest to keep a straight line with. Of course this has to be countered with the amount of kayak that can get pushed around by the wind, and a longer kayak = more kayak to carry around. For a kid or young teenager, I would look at kayaks that are 12' - 15' long. For adults, I consider 14' - 15.5' to be a great length for day-tripping (long enough to move efficiently through the water, short enough not to be more boat than is needed). My 15 year old now paddles a 16' kayak (Wilderness Systems Tempest 160 which is a good size for the smaller-framed adult) for day trips and camping trips.
In short, there is no one right answer but the better that any paddler fits their kayak, the happier and safer they will be.