The Lord further promised that after He destroyed the city by deluging it with great waves of invaders (cf. Ezekiel 26:3), it would die like a person placed in a grave (cf31:16; 32:18 , 23-25 , 29-30). It would go down into Sheol, as it were, and so lose its glory. He pictured the island fortress as submerged beneath a sea of invaders that would bury it (cf31:14-18; 32:13-32; Isaiah 14:4-21). [source][source][source]
"The most fearful prospect facing ancient mariners was to be caught in a storm and be "lost at sea."" [1][source]
Ezekiel mixed two metaphors for destruction in these verses: waves overwhelming a rocky seaside town, and a person going into the grave (pit, Sheol). [source][source][source]