Readings & Meanings:
I walked, following the shore.
You have to cross in a boat to the other shore.
I picked up shells from the beach.
They are making a levee protection at the riverbank.
山 is the radical.
厂 (cliff) surrounds the phonetic, 干. As 干 means a stick thrust against an enemy, this signifies that the shore is the ground that sticks to the water.
山 serves to show that it's high ground (higher, at least, than the riverbed or ocean floor.