Cleon
Legend
This isn't exactly what I was seeking, but we might be able to mine it for ideas...
Swift Glide (Ex): When moving its full base land speed, a tybor floats several inches off the ground. This allows a tybor to move unhindered through slick or dangerous terrain. A tybor may even run over the surface of water. This ability lasts as long as the tybor continues to move at its full base land speed, though if it is not on solid ground at the end of its turn, it will suffer the effects of whatever it is standing on. A tybor must move at least 20 feet in a straight line before it begins to glide, though it need not so in subsequent consecutive rounds when continuing to glide.
This was more what I was looking for, if we remove the gaseous bits:
Gaseous (Ex): A moor hound's insubstantial form grants it several benefits. A moor hound doesn't actually fly, but floats just above the ground. As a result, it is not subject to ground terrain effects, such as ice or a grease spell, but it is subject to winds as if it were a flying creature. It cannot wear armor, manipulate solid objects, or enter water or other liquids. It can pass through small holes or narrow openings--even mere cracks. It also can occupy squares occupied by enemies.
So something like this:
Ghostwalking (Su?): A ghost mount can float just above the ground. It doesn't actually fly, but is not subject to ground terrain effects, such as ice or a grease spell, and is subject to winds as if it were a flying creature.
Should they be able to ghostwalk across water?