Build a damn, dummy. Or at least start putting the water in your inventory to buy you enough time to GTFO the way.
Why hasn't the MC just grabbed the Guide and filled his airways and digestive tract with sand already?
Why hasn't he used the sand he's dug to fill in the pit trap while he walks around in it so he can walk out when it gets to the top?
Why hasn't he started making sandstone or other sedentary/metamorphic rock out of the sand and building with it. Packed sand is a shit construction medium.