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Based on the design of stepper motors, having no exposed electrical parts, is it then conceivable that they will work submerged in water or other fluids?

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Unless the bearings have waterproof seals , the bearings will rust.

Disk drives use ferro-fluidic seals to seal out all air.

So you cant simply use ANY stepper motor because there is no commutator. But they do exist. Oil filled double O ring steppers. http://www.empiremagnetics.com/prod_wat/prod_wat_stepper.htm

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I'm not sure about the hard drive thing. Old drives had a small hole with a filter over it to allow the air pressure inside to equalize with the outside air. Without this the hard drives would literally blow a gasket if taken to a high altitude, like Denver. One of the innovations with 3.5" hard drives was some companies stopped using the hole/filter and instead used the bearing itself for gas exchange. I have no idea how they kept the dust out. – David Kessner May 25 '12 at 18:42
I was sure about the hard drive thing when Ken Wing Director Seagate QA offered me a job from Canada when he got promoted to VP in Scott's Valley , CA in the 80's. The filter hole contains a HEPA 99.99% filter. There is also a wedge filter inside to trap airborne contaminants. Due to altitude, the Drive cannot be sealed to air pressure otherwise the ferrofluidic seals would leak all over the disks. There may be exceptions to this now as you suggest. When Seagate was making 200K drives a month in Singapore, I alerted them to a problem. They flew me down and I prove their production test was bad – Tony Stewart May 25 '12 at 18:52
They use a laser particle counter to measure interior dust levels using 10cc/sec and that was like a hoover air cleaner... so they always read zero.. I used the same equipment but adjusted it to 1cc/sec and the particle counts rose to several hundred/cuft. Seagate stopped the production line for 24 hrs and designed a shield for the bearing, in spite of low RMA counts and were back up and running. That's one of many reasons why I know so much about disk drive designs. I reverse engineered everyone's product in order to select the best design for Burrough's OEM products. in the 80's. – Tony Stewart May 25 '12 at 18:56
IF I remember correctly, I read about this in EDN in the mid 1990's. It was about Western Digital. However, I could certainly be remembering things wrong-- it's happened before. :) – David Kessner May 25 '12 at 19:42
that was after my era in HDD technology. They use glass now instead of cobalt doped oxide over aluminum. I even had serial number 8 of Maxtor's 1st 80MB 5.25 drive in a shoebox. Servo recal, always was funny sounding like R2D2. But great design. Owned by Seagate now) – Tony Stewart May 25 '12 at 19:45
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up vote 3 down vote

It will work if you have an underwater stepper motor!

Most stepper motors are not designed for underwater use, and if it doesn't say so in the datasheet then you must assume that it won't work.

Just because the motor does not appear to have exposed parts doesn't mean water can't kill it. Motors have seals and bearings that water can get into and destroy. The lubricants used on the bearings don't always work with lots of water. The motor shaft and bearings can rust. Etc. There are lots of ways that water can damage a stepper motor.

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