Well I only DJed on very big cruising boats, but I guess some stuff does apply, so here what I learned:
– Do not play as loud as you would in a club, people will still dance, but also like to talk and sound does carry there as the water reflects it also
– Prepare for longer sets and also have some “chilling” music ready. I like to play especially some cool belearic stuff before the main set and combine belearic and deep house for chill out for those people that won’t go to sleep…
– Do not drink too much, you will get seasick if you do
– Drink plenty of water and also eat something, low blood sugar is #1 reason for sea sickness as people think if they do not eat then there is nothing to come up…. very wrong…