It helps to have a rug on the floor so they have starting traction for their flight. Cats seem to sleep all the time. Cats sleep when you are awake. They get up when you go to bed. A boat is a fairly confined space so many times they like to hold dancing practice on your bed just as you are dozing off.
Many marinas have resident harborcats.
These cats have their established territory and your boat will be in the middle of it. It is guaranteed that they will smell your cats and visit your boat in the middle of the night. Your cats will be found on the chart table looking out the window with 1 to 10 harborcats on the other side looking in. All will be expressing their thoughts verbally at the top of their lungs. You then consider using the crab trap for other than its intended purpose, without telling the Admiral.