Moorhen chicks

I live on a boat and a family of moorhens has been nesting on my back deck. The chicks have all hatched and seem ready for fledging as they are wondering about on the deck but they can’t get into the water as there is a big lip on the deck about half a foot tall, so it’s like they’re in a little pen. I really don’t want them to get overheated or weak without access to the water but don’t want to interrupt the situation. I’ve given them a plate of water and a ramp to get into the canal, but I’m worried they’ll do it one by one and get separated. Can anyone advise on this rather strange situation? I think it might be best for me to put them all over into the water at the same time but then there will be no way of them getting back onto the boat. The chicks are 5 days old now. Thank you!