Finding north, in the real world, is relatively simple, and can be accomplished by a number of means, day or night, regardless of terrain. Even at sea. DC:5 isn't that far off.
As I have pointed out before, however, knowing where north is DOES NOT tell you where you are! If you are blinfolded, flown to parts unknown, and then dumped off the airplane with a working compass (even one corectly set for declination), it will not tell you where you are! What it WILL do, assuming you know how to use it, is to start from where you are and set a course, being able to reverse it to return to where you started (assuming you memorize or record it).
No, Survival (Wilderness Lore, in 3e) will not allow you to sail the ship. That's what Profession (Sailor) is for.
Knowing which way the ship is going is certainly possible with Survival/Wilderness Lore, as are determinations of speed and distance. The ship's Log (not the Captain's Log Book, but the Ship's Instrument) can tell you that, as can simply dropping a floating object off the side of the ship, and observing it... Of course, figuring out how to USE the Ship's Log might require some Knowledge (Architecture & Engineering), or Profession (Sailor)... or maybe just an INT check.
One thing that certainly CAN be done is to determine the Latitude that the ship is at and (assuming the ship is sailing east or west) sail across that Latitude to the opposite shore. This can be done with only the north star visible, and without ANY instruments (to within 1 degree of accuracy). Determining Longitude is tougher, requiring accurate determination of the time of noon, and passage of time (which, in D&D, is done by magic... I forget the spell's name).
Anyway, Profession (Navigator) would be the best way to determine what's around you in the ocean, but with charts, compass, etc., a decent woodsman should be able to keep you from getting lost. Of course, if the GM WANTS you lost, there are always hurricanes, monsoons, typhoons, waterspouts, behemoths with
Swallow Whole, etc.
Knowledge (Nature) can also cover prevailing winds and currents, allowing Druids and Rangers to do some good, shiny, day-saving (with the proper rolls).
Pretty much anyone can maneuver a small ship, when in sight of land, and/or when sailing across the ocean on a single Latitude. The Vikings proved that, in their klinker-built longboats (with square sails). A skillful Druid, Cleric of Travel, or Ranger could probably do at least as well.
Need to find north? a shadowstick or lodestone will point the way! (Not to mention an actual compass, or a needle passed through silk, or...) Need to determine your Latitude? All you need is the north star, and your two hands! Need to determine where you are? Knowledge (Geography) will tell you, and Knowledge (Nature) might allow you to deduce it. Knowledge (Nature) will also allow you to determine prevailing winds and currents, for the current season.
Profession (Navigator) is still your best bet, at sea, though... And Profession (Sailor) will be needed to make the ship go. Of course, you could always just kill ALL the pirates, level up, and take a rank...