What are the in-game effects of the Guard power? Other than the blanket 'prevent a glitch from occuring', what is it good for?

Can it protect you from drowning in the ocean - is it effectively water breathing? How about pressure from deep waters and the associated damgers (nitrogen narcosis, etc.)?

Can it protect you from flames in a forest fire? How about from smoke inhalation or glare?

Can it protect you from environmental radiation?

Can it prevent falling damage?

Can it prevent enviromental disease transmission (tainted water, etc.)?

Please give me some feedback on what could be either just fluff or a very powerful ability.

"The Guard power gives the critter the ability to prevent normal environmental accidents and hazards (both natural and those induced by the Accident power), such as preventing someone from succumbing to heatstroke or saving someone from drowning. The Guard power can also be used to prevent a glitch from occurring."

Purely by the RAW...

Yes to all of the above.