Can an Unseen Servant act as a deckhand?

Question

The unseen servant spell can perform "simple tasks", and "can’t perform any task that requires a skill check with a DC higher than 10 or that requires a check using a skill that can’t be used untrained"

To sail a ship effectively, you need a certain number of deckhands performing standard actions each round, doing miscellaneous ship tasks. There's no check required for these deckhands, but if there were it would be Profession Sailor, which cannot be used untrained.

So, can an unseen servant act as such a deckhand?

Answer 1

No

To quote the potential showstopper first:

It has an effective Strength score of 2 (so it can lift 20 pounds or drag 100 pounds). It can trigger traps and such, but it can exert only 20 pounds of force, which is not enough to activate certain pressure plates and other devices.

While today's sailboats work with all kinds of tech that may make this possible, in the Age of Sail (which is more modern than most D&D settings) this would not fly. 20 pounds of pressure is nothing. That's not enough to lift a lazy cat up, it's surely not enough to be a deckhand.

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That said, yes, all tasks for a deckhand are "simple", but if you needed to command each and every one of them (like with a crew of landlubbers) the commanding officer would be hard pressed to actually get any sailing done. While that's not so bad with humans, because they learn, you cannot sustain that with a "force" that only follows orders and never learns. This is what the "Profession: Sailor" is about: knowing what simple tasks to combine to follow an order without the captain explaining every pull and push of every rope in detail.

So even on this grounds, the answer would be no, because

It can’t perform any task that requires a skill check with a DC higher than 10 or that requires a check using a skill that can’t be used untrained.

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However, having ships crewed by magic is cool. And you are free to research mightier versions of the unseen servant, either as player or DM. For a cool ship you will want Permanency anyway, so maybe you can find "Mordenkainens pretty much improved servant" somewhere, if you look hard and ask your DM nicely.

I'm sure products have done this already. Probably with lots of handwaving the rules, but it's your game. If you think it's cool, go for it. A necromancer should be able to raise the dead to do it, unseen servants of around that spell level should be able to do it, too. After all, such a ship is more of a story thing and not really unbalancing anything.

Answer 2

Yes.

Assuming use of the Stormwrack supplement, the description of the Profession (sailor) skill (p87), as noted in the question, requires checks from the character directing the boat or ship, not the deckhands. Indeed, the description of the helmsman seafaring role (p82) says:

...deckhands who are on watch handle the helm as directed by the conning officer (whichever officer is currently in charge of keeping the ship on its course).

Skill checks for the handling of the ship are generally made by the person commanding the helmsman, not the helmsman himself...

Additionally, the spell Mordenkainen's capable caravel (p119) says

The ship is crewed by a minimum complement of spectral deckhands, which perform the basic tasks of maintenance. These ... behave as unseen servants but can travel anywhere on board ship and can enter the extradimensional space if you so direct. The spectral deckhands respond to the direction of the helmsman, reducing the number of crew necessary to control the caravel to 1.

This suggests that yes, as long as the caster of the unseen servant spell, who is the only creature that can usually direct them, is making the Profession (sailor) checks to direct the crew, unseen servants can perform the duties of deckhands. Note that their 2 strength might limit their ability to perform the duties required.

Answer 3

Ask the DM

The 1st-level Sor/Wiz spell unseen servant [conj] (PH 297-8) says that it creates an effect "that performs simple tasks at your command" and follows that with a list of tasks the effect can perform, but this list isn't exhaustive. Nonetheless, as the question notes, the effect "can't perform any task that… requires a check using a skill that can’t be used untrained."

Stormwrack on Seafaring Roles an entry for deckhand which says

Most of the sailors on a large ship are deckhands—that is, able-bodied seamen who handle the ship’s sails, lines, small boats, and deck maintenance as directed by their boatswains or officers. Deckhands generally are commoners, experts, or even warriors with 1 to 3 ranks in Profession (sailor) and 1 to 2 ranks in Climb and Use Rope. (82)

With this in mind, the DM may rule that even pedestrian deckhand tasks require at least 1 rank in the skill Profession (sailor). However, what that generally means in that deckhand description sentence is up to the DM, and a generous DM may rule that the effect of the spell unseen servant—perhaps if the effect is closely supervised and given step-by-step insturctions—a perfectly serviceable replacement for a conventional deckhand. (As this latter ruling allows ships crewed by other mindless creatures like typical skeletons or crewing an entire ship by using the 3rd-level Sor/Wiz spell servant horde [conj] (Spell Compendium 182), this DM gravitates toward that latter ruling because it's cool.)