There does not appear to be an explicit general rule. From circumstantial evidence, it looks like Floating Disk is visible.
Can you control tenser’s floating disk?
No. It isn’t described as having any weight, but it is described as immobile in it’s description, at least while it is within 20 feet of you. Immobile could mean it stops moving on it own. It could mean nothing can ever move it.
Can you use tenser’s floating disk as a shield?
Any party that has spent hours trying to cross a river can appreciate the effects of this spell. So long as the caster has a means of bypassing these barriers, then they can slowly drag their pals along. Tenser’s Floating Disk has other uses outside of its intended purpose, such as a shield for prone characters.
Can a floating disk move across a liquid?
It can move across uneven terrain, up or down stairs, slopes and the like, but it can’t cross an elevation change of 10 feet or more. As such I do not think the disk is meant to cross liquids. Anything between liquids and solids is undefined and up for DM adjudication.
Can a tenser’s floating disk move under its own power?
No. While you could command your Tenser’s floating disk to move close enough for you to sit upon it, it has no ability to move under its own power. It can follow you only at a maximum rate equal to your normal speed.
Is there a first level spell like Tenser’s floating disk?
Another first level spell exists called Mount that is comparable to Tenser’s floating disk. Depending on your need, maybe better. It is also a first level wizard spell. There is nothign to stop you from loading up your mount with jewels or gear, like you would a Floating Disk.
Can you ride Tenser’s floating disk in RuneScape?
There exists a 4th level spell called Greater Floating Disk (Spell Compendium, Pg. 96) which has a fly-speed of 20-ft. and specifically says in the spell description that it allows characters to sit on it and ride it. You could certainly ride it, it just has no propulsion of its own.
