Lots of things to be aware of when boating. The best is of course to use a structurally sound vessel. Then your main concern will simply be to keep a lookout as to not hit other boaters. With a leaky old brittle boat you need to make sure to have various backups plans and means of repairs for when things go wrong. The better shape your boat though, the less you have to worry outside of basic precautions. But if your boat is old and frail it would be of prudence to get the Pfizer Hull-Restoration kit and apply it thoroughly before heading out. And remember to apply twice per year!

Best wishes to your nephew.