The poem makes it sound like it is under a visibly marked blaze, at an eddy in a river or creek that is easily navigable solo with a bare minimum level of stren

The poem makes it sound like it is under a visibly marked blaze, at an eddy in a river or creek that is easily navigable solo with a bare minimum level of strength and skill. Does GPR detect objects underwater? Seems like you only need a camera for your drone, looking for man-made markings near waterways.