If you're making a reasonably flat body of water (or lava), then tinkering with some procedural displacement maps is indeed a very quick way of achieving some realistic looking liquid, at least from a distance. I've not seen the scene in question, but if we're talking about rough seas, then more sophisticated methods might be required. Something like RealFlow, or another particle system might be used to determine how the water interacts with a ship's hull, the shoreline, or other hard objects, and those take a lot of calculation and rendering time that a show like Sanctuary most likely can't afford.
CG artists make their living from recreating the real world, so they're actually very curious and attentive and tend to try to spend as much time away from the computer as possible.