User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-12265783-20130831144217/@comment-26074976-20130831150629

To fully upgrade your boats you need to trade with Argosy Captain with Rare Trades. Legendary Tides and Pirates Tomb are accessible when your Boatman says "We have made a few upgrades to journey somewhere new" or something along those lines. I maybe see it 3 times a week if I send them out everyday. As for Blue Cutthroat I suggest using Fish Finder and sending your boat to Moga Deep when they suggest to go there fishing. I caught a spear tuna but cannot remember how I even got it. Still need to get another! Hope this helps!! :)