In general, the cargo. If there's a few boxes and barrels, then their trip would've been relatively short, as opposed to lots of boxes and barrels, which would indicate a longer trip. Although, if the ship looks absolutely wrecked, the amount of cargo won't indicate the length of the trip, as extra cargo tends to be thrown off in a storm so as to lighten the boat. Now, some specific things on the ship would show more details of the trip on that now-sunken ship would have been like. For example, the amount of barrels containing gunpowder (not that it would've been preserved; the water would've gotten in at some point) is indicative of their expectancy of pirates, or other ne'er-do-well's on the sea. The crew's quarters (or lack thereof) would help to show how well (or not) they lived. Another would be the things that wouldn't (or would) have been on the ship from their port of origin; treasure, etc. Maybe they have spices, or gold, or ceramics. This would show where the ship had been going (or coming from).
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