Forgot to mention, the yacht will need to be registered on a national registry. Also, as some have noted above, radio licences are required for some types of radios. And of course visas will need to be obtained for all counties visited that don't have a reciprocal arrangement with your passported country, including those of all crew. You'll also have to make yourselves aware of notification requirements. e.g. Customs MUST be notified 96 hours before making port in Australia otherwise big fines will result. Other countries, other rules. It's all fairly tedious.
You also need to clear out of