LEGO's electric or electronic parts are usually not waterproof, with a small subset that was explicitly designed for such use in a few nautical-themed sets between 2004 and 2007. These motors feature no open contacts, integrated battery holders and gaskets along any seams to provide water sealing.
The components you ask about have open contacts, no sealing - and even if they did, the radio waves required to operate them underwater would be greatly diminished by the physical properties of water to the point of unusability at even minor depths. They were not designed to be used in any kind of wet environment, including fog or rain. Surprisingly, I haven't found any kind of official warning to this effect in the building instructions, but if you'd like, I can ask a representative of LEGO directly.
If you're really intent on using the motors near or in water, you'll need to either build a structure which guarantees that the batteries and motors will always stay above the water line (including any waves and spray) even if the boat rolls or capsizes; or build some kind of waterproof enclosure for them. Beware though, neither of these is an easy endeavour and any mistakes during design, building or operation could easily ruin both the hub and the motor. But there have been people who managed to achieve success with both of these approaches, so these are definitely doable - just with significant planning, engineering and tinkering and at no small risk.
