In the one piece modpack you can build your own ship using blocks from the Eureka! Ships! mod. All you need is an anchor (which you can search up in your inventory using JEI mod) the blocks you want to use to make the ship. If you don't feel like making your own ship you can craft a prebuild one using the Small Ships mod which you can find by searching it with JEI.
There is also a lot of exploration in this modpack in which you can find dungeons with rings in the chests that you can equip for a small boost to yourself, or you could find a marine base with a wooden, iron, or diamond chest in it which can give you your very own devil fruit (to open the chest you need a golden key).
I have also added the Ice and Fire mod which gives you a pseudo like boss such as dragons which you can slay and use there scales for better armor. There is also an Otter mod which you can tame your own otter, called Ottercraft.
If you have any questions about the mine mine no mi mod or any of the other please ask them. I will be happy to help.