Klarense is a sailor involved in the Dragon Slayer quest and he is found on the second most southern dock of Port Sarim. He sells you his boat, the Lady Lumbridge, for 2,000 coins, which you need to sail to Crandor.
Interestingly, after the quest, Klarense gets a new ship (identical to the Lady Lumbridge). When asking about the new ship, the player will say they are able to see where Klarense has painted over Lady Lumbridge and written "Klarense's Cruiser", Klarense promptly responds "Nope, you're mistaken. It's my new boat".
The only way of reaching Crandor after the quest is by taking the route under the Karamja Volcano. Klarense may be right in fact, because the Lady Lumbridge is still there. However, Ned is too, but, when going back to Draynor Village, he is there as well.
You can buy the Lady Lumbridge only during Dragon Slayer. If you ask him before embarking on the quest you cannot board to fix the Lady Lumbridge. He will also tell you that "The ship is not ready yet and Port Sarim's workers are slow so there's no telling how long the ship will take to fix."
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