We cannot advise you on which documents you will need, as this depends on your nationality and the country you live in.
The VisaHQ website can tell you exactly what you need. Remember to include the countries that you might travel through to get to your final destination as well.
You will need your passport details to check-in online, but we do not require your physical passport to board the yacht.
If you are travelling through the Schengen area and are using your ID card, this is fine as long as you have entered your passport details into your booking profile before departure.