In Finland collectors frequently set traps to the outermost rocks by the open sea, in order to catch migrants that cannot live in these places. Sometimes thy acquire huge quantities of migrant moths, and also butterflies, especially Vanessa atalanta as bait traps attract it well. I know this is not a boat, and the Finnish landscape differs likely drastically from your area of interest, so perhaps this is not of much help. Rinaldo's suggestion of light traps is feasible, and bait traps perhaps even better. But, I have never seen literature on trapping on boats which was your original question. Occasionally moths are found in boats and ferries (like Phlogophora meticulosa), but these are more anecdotal notes than organized studies.