It depends what size the pods are. And I assume you meant there is "something alive inside" of EACH pod. If they are the size of chicken eggs, then it's most likely a clutch of alligator eggs. They dig a hole near water and lay their eggs in it, then bury them.
it might be spider eggs
Cornus canadensis
Truffles grow under the ground.
It depends on how you would like your watermellon to be after it is done growing.
By growing peanuts in your ground.
Hydrogen sulfide has a smell not unlike that of rotten eggs. If this is accompanied by a large, growing crack in the ground, a volcano is growing.
Grass
Grounding was an issue in many Jeep Wranglers, check the ground connections behind the gauge clusters first.
its their way of growing
Something which is perpendicular is at right angles an example would be that a tree growing straight out of the ground would be perpendicular to the ground. Things are parallel when they run along side each other always the same distance apart, an example would be railway tracks.
Cantaloupe develope on a ground-growing vine. Because it grows on the ground, it cannot "fall" for it is already on the ground. Complete folklore.
Sphagnum moss.