I disagre with the blanket no-nos expressed by other posters. If used right, a car seat or bicycle seat is an added safety resource on an reasonably large boat. It's also used widely here and I have never ever heard of a serious accident.
The reason is this, more important than floating, is actually staying on board. That is why also adults are secured with harnesses and life slings.
It's very rare for a boat of reasonable size to suddenly sink or capsize. Granted, this is somewhat related to boat type and size, but an average sailing boat with a keel doesn't capsize at all and very rarely sinks.
Most injuries are from falling while moving on board or getting in the way of moving parts. Most drowning incidents are from falling overboard. Those risks are greatly reduced if an infant or toddler is secured.
For those that have any actual experience from over-board rescue training knows too well that it is very difficult to get even a fully cooperative adult back on board in all but the best weather conditions. Therefor, many sailors implement the "staying on board principle". Basically it means that securing yourself to the boat when weather conditions requires it is more important than wearing floatation devices.
We used an infant bucket last year and a Britax TWE this year, and it works great. DS can sleep without us worrying if he will fall or get hurt when we tack or get wake.
Remember though:
- He is either in the seat or in the life vest!
- Don't transport children on or off the boat in the seat!
- The seat must be securely attached to the boat!
We use the Helly Hansen KidSafe, which generally performs best in test for kids still in diapers.
http://www.flytvast.nu/helly-hansen-kidsafe.html
http://www.hellyhansen.com/product/Floatation/Kidsafe/33814/view/272
The USCG site was no help at all, they basically had no advice to give on small childen on boats. "
The Coast Guard does not recommend taking infants onboard a recreational boat"... (!)
I do agree with their advice about testing the PFD in a swimming pool. We have done that and it works as intended. I also strongly recommend baby swimming classes which is a great way to make infants & toddlers more accustomed to water and reduce the risk of panic if they should fall in.
http://www.babysim.com/uk/aboutbabyswim.htm
Erik is rear-facing (of course... !) in a Britax TWE on our HR39.
BR /Marcus