As I am new to these forums, I don't know if this has been addressed before. My apologies if it has! I have recently found a strategy that seems to work very well when attacking on a voyage. Here is what I do: I decide what I am going to attack on my voyage. Then I go to the tavern and recruit the units that likely will work best. I recruit the most important ones first and then the others. I return to the map and lay out the voyage as planned. Naturally, the "suicidal!" warning appears. I then patiently wait as the recruits join the crew. Before long, the "suicidal" label changes to "dangerous" and then as the crew increases, the label disappears. I usually allow 2 or 3 more crew to join and then set sail. Almost always, my journey is successful! Most recent trip was to lower left and the 3* bigger fish. Crew recruited was: Chih Shih 1 WD 7 Gunners Success in defeating fish with 1 Gunner left and both EP and BP obtained. FWIW, try it out.
Hey, SaK! Thanks for your comment. Look forward to hearing your experience and any refinements you can suggest.