I am very prone to serious seasickness and I cannot wear a patch; I tried it once and had some severe side effects, but I have taken more than a dozen liveaboard trips and I loved them.
In my experience I am most likely to get seasick if the trip involves a deep-water crossing (like Florida to the Bahamas). I have done 2 liveaboard trips in the Turks and Caicos and I didn't get sick on either of them because we just traveled from Provo to West Cay and French Caicos. We did both T&C trips in the fall when the water is warmest.
But I have been very sick on some liveaboard trips that required a deep water crossing (St. Martin to Saba was a rough one) but my experiences have been that I am only sick for one night and then I start to acclimate, and after a day I will be just fine. I have even been through some storms at sea and didn't get sick after I became acclimated. When you are diving land-based dives, you are on/off the boats and you never really get acclimated, but when you are on a liveaboard your body has time to adjust to the new reality. It just takes some of us a little longer than others!
Here are my techniques for reducing the risk of seasickness on a liveaboard. I don't eat/drink much on the day of departure. I take the seasickness medication before I board the boat. When we get on board my husband and I split up to try and get ourselves situated before we leave port. He heads to the dive deck to set up and stow our equipment. I head to the cabin to unpack our belongings and then to the salon to complete any paperwork.
After we depart, I stay up on deck with the cool air blowing on my face and I watch the horizon to help my eyes and brain adjust to the motion. If I can tolerate it, I try to sip water to stay hydrated. I have been known to spend the first night sleeping in a lounge chair on the upper deck and I am usually not alone.
Sometimes the precautions work and I just feel queasy and headachy, but I have also had some miserable first nights with violent vomiting, even when there is nothing left to throw up! But again by noon the next day I feel fine and I stay that way throughout the trip.
Everyone is different but the only way to find out is to try, and I think the T&C liveaboards are a good way to test your sealegs. Just a precaution, be careful not to overdue the seasickness meds, or mix them with anti-histamines because you may increase your risk of side-effects. If you are wearing the patch check the paperwork that comes with it to see if there are any precautions about taking other products. Good luck!