We have two children ages 4 and 20 months. When our eldest was 18 months we sailed from cape town to rio via st Helena. We made a decision to not use a life jacket on her as we felt going in the water meant she was dead so we instead focused on keeping her on the boat.
We made one adjustment to the boat by welding on two attachment point at the base of the cockpit so that she could be attached there and have access to the full cockpit but not be able to climb out due to the tether length.
We also had a set of rules we followed religiously..
1. She was clipped in before she left the companionway
2. She was not allowed outside the cockpit
3. She was not allowed into cockpit if the conditions were rough, seems common sense but little ones want to be where their parents are and ours always wanted to be outside so would make quite a ruckus to be let out even when conditions were not great.
The fear of a small child falling overboard at sea should be dealt with by having appropriate rules,
equipment and training but it it really the least of your concerns when sailing with small children.
They are far more likely to be hurt badly in a fall during bumpy
weather or to drown while in a marina or off the hook.
We had terrible
weather for an extended period on the passage from st Helena to rio and thankfully had rigged an attachment point in the salon for a car seat that allowed us to secure her in there if the boats motion was excessive, which it was for over 10 days straight, and also if we both needed to be on deck for any reason we could secure her in there, and pay dearly for it with her screams of protest.
It is not when we are vigilant that our children get hurt it is when we feel safe. Most deaths of children in the sailing community happen in
marinas. Not two weeks before our arrival into Niteroi in Rio a child aged 5 was unsupervised playing with other children and fell off the dock and drowned. While in cape town a 6 year old fell in and the wind blew them away from the dock and only pure fate was a rib in the water to pull her out. Neither of these incidents were the parents aware of until after the fact.
Edit: another death in
brazil in bahia de ilha grande happened with a couple with a fully netted boat like ours that were asleep at
anchor with their companionway
hatch open as we all do to keep the air flowing. Their 4 year old climbed out onto the deck and over the netting and fell in the water and drowned while they were sleeping.