I have this idea for a specal kind of travel power devices:

* Gravity Generator: Creating a stable gravity field around you, this device, while avtivated, allows you to move anywhere as if you were walking on the earth's surface. Very useful underwater or on the moon. ;)

* Moonwalk: Creating a low-grav field around you, this device, while activated, allows you to jump much higher than normal and slows down your fall, making you immune to fall damage. Does not work underwater (as it is based on land physics) or on the moon (where you get the low gravity effect anyway)!


These devices modify physics, but are no real travel powers. You can use them together with some travel powers, others disable their effect automatically. For example; having the Gravity Generator active allows you to jump and run underwater as if you were on land, including using Superspeed, Superjump, Acrobatics, Tunneling or other land-based travel powers, but it does not allow you to use any kind of Flight. Instead, your character uses accelerated swimming, just as if the GG wasn't on. That is because the device manipulates the envoirmental movement (changes water to land physics), but has no influence on how the envoirment modifies travel powers outside the device's range. (Flight powers = aerial physics. The device changes water to land, not water to air. Therefore, it has no effect in this case.)
Short: It makes land-based travel powers work underwater just as they would work on land, but Flight (including Teleport) powers still work just as they normally do when used underwater.

And just to make sure: "Physics Modification Devices" are not meant to be used together. You can only have one active at a time. This is to avoid complications that are quite likely to occure when mods collide.