Oh my goodness....first off your ship is huge- it is not like a tiny little sailboat. Even in a storm you are fine. ( I was on a ship on the outskirts of a hurricane...only had some mild rocking, it was not bad at all)
You are probably safer on a ship and a plane then you are going to the grocery store.
Think about your fears..for example you mentioned drowning...are you planning on jumping off the ship into the ocean? Since I am guessing the answer is no so then how would you drown?
Trusting someone else to do the flying and driving the boat is what you have to do...they do this all the time, it is their job. Unless you know how to do those jobs then you cannot "control" it.
Living in fear is not living...it is paralyzing. It may help to seek help for irrational fears- especially if it begins to take over your life. It is great that you are going to take this trip! Relax and enjoy it. It is worth it to try new things.