On ships the netting is to keep a big wave from washing
if it knocks you down. And it does work
. For a small dog and a toddler, it will keep them from going under the rail. But it won't stop a climber or a jumping dog. Even with netting, I had a big dog jump overboard
. My dog doesn't wear a life jacket, but a toddler, I'd keep tied to something or make a space with high netting he, she, it couldn't get out of.