Do you use Ride or Nature Lore for boating skill?

Nature Lore. Riding would only apply if you were, I dunno... riding a shark or something?

The Enemy Within suggests Coordination in its overland travel rules.

The boatman has the following skills: Athletics, Coordination, Nature Lore, Observation, and Resilience. I'd definitely use one of those.

I guess it depends on what kind of boat/ship you're on and what your job is. Athletics if rowing a boat, to steer a ship observation or nature lore might work. Working on a ship might be coordination or athletics depending on specifics of your duties.

Probably you could make a couple of rolls with a couple of different skills. A captian might roll observation to avoid reefs and other dangers and then nature lore to navigate by the sun and stars, while a deckhand might roll athletics to hoist sails and coordination to climb in the masts. A lookout in the crows nest obviously would roll observation.

In bad weather resiliance may be used to avoid sea sickness and coordination to keep from falling overboard.

Yup a boat and particularly a ship is not a "one skill" thing but multiple skills, which can actually be fun as it allows different players take on different rolls. One Observation to spot "Iceburg straigth ahead!", one Athletics to pull hard on the tiller to shift course, one Coordination to dance along the ropes and yardarm to shift the sails as needed....

This is helpful. Thanks everyone. I wasn't sure how I was going to handle this either, so the examples were really useful.

Another way to answer some questions about various things is to just use the Career.

You're a Boatman or completed that career, congrats you know how to use your skills and tell others to manage the boat (there is no Sailor career, I use the same one), just as the Roadwarden knows about the "law between cities and noble holdings in his province" and the Witch Hunter knows about what his writ allows or doesn't, the Servant knows where to get stuff cheap - the actual "career" often isn't used enough except for magic-wielders and should be treated almost as its own "specialization or fortune point to spend".

I agree with valvorik. A character who's with his/her occupation (career) should be able to handle routine stuff which falls into the careers scope. A boatman might not need to roll at all when working on a boat, as long as all other factors (such as weather) are routine.

But when all goes to hell (storm, pirate attack, cthulhu rising, dragon attack or a battle etc.), even the boatman should roll.