What gear do you actually need?
Gear is expensive and deciding what to purchase is usually tough.
On a Yacht there is a "must-have list" in my opinion.
A GoPro can take images that will blow your guests away IF you know how to get the most out of your GoPro. Its small and unobtrusive, Its durable and image quality for video and photos are impressive. It is a must-have. I only recommend GoPro hero 7 or Hero 8 due to the stability of the video.
Drone footage will likely be what your guests show their friends and families. It provides perspective and is easy to use to wow your guests.
DJI Mavic ZOOM - Great way to fly further from the boat to remove drone noise but zoom in to be close enough to see everyone having a good time.
DJI Mavic 2 Pro - Higher quality images, ability to crop images better and still have clear photos, better low light capabilities for sunrise and sunset.
My suggestion is to start with the two bits of gear above. If you find yourself taking images of the guests up close, you should consider using a professional camera.