On: Save the dog from a 70m deep, 35cm wide hole

[zeteo]

Slowly fill the hole with very salty water. The dog will float to the surface.

The stated dimensions will require about 7000 gallons of water. This is the capacity of a large-ish tank truck. 70+ meter hoses should be readily available.

[gydfi → zeteo]

It's a dirt hole. My guess is that you create a large amount of mud at the bottom of the hole and then the walls collapse.

[Semiapies → zeteo]

Presumably warm extremely-salty water, or it might get hypothermic.

However, if it's somehow wedged in there, the dog could drown.

[gmarx → Semiapies]

I think you need to get a camera down there to monitor the progress of the solution

[gmarx → zeteo]

Or sand

[fimdomeio → zeteo]

or mythbusters style fill with ping pong balls. Probably both bad ideas.