For my initial Idea of the characters I like to do a ton of quick thumbnail sketches such as these. In this panel I've laid out several thumbnails of the protagonist (left) and the antagonist (right). Sense I wanted the protagonist of the game to be a little more frail I did most of his designs with a much more slender build. He's meant to be strong, but he's not that strong. His overall design is also very simple. Since he's become a drunk, after losing his wife, he doesn't carry much around with him. Perhaps a bottle of booze and a few hand tools used in sailing.
The Antagonist on the other hand is a fearsome pirate captain with a burly build to him. I wanted him to look much more powerful and so I gave him extra heft and much weightier clothing. He's a very materialistic individual therefore his overall design is much more complex than the antagonist's. I pulled some inspiration from samurai garbs as well to try and give him more visual appeal.