A swimsuit should be at the top of your packing list, as this is the only way you can get in the water. Also, bring a sweater or extra layers during cooler months or evening parties, and never forget your SPF and lip balm to prevent sunburns.  Although most yachts provide guests with a towel, bringing along an extra one will help you stay comfortable throughout the day. Besides keeping you dry, a towel can be used as a mat to lie down and relax on or as a cover-up.  But, the most crucial thing is to bring a great mood, as no amount of party supplies can assist you if you\\'re not in the spirit.