When I shall bring thee down, etc. The pit is sheol, Hades, the unseen world of the dead. The image may have been suggested by Isaiah 14:9, where it is used of Babylon. It was obviously one on which the mind of Ezekiel dwelt, and is reproduced in Ezekiel 32:17-32.
Here, apparently, the sinking in the depth of the waters (Ezekiel 32:19) is thought of as leading to that world of the dead that lay beneath them. The people of old time may possibly include the races of the old world that were submerged in the waters of the Flood.
The imagery of Psalms 88:3-7 seems to have been floating before the prophet's mind. I shall set glory; better, will set. The contrast drawn is that between the shadow-world of the dead, and the earth with its living inhabitants.
There Jehovah would establish his glory, would, sooner or later, manifest his kingdom, while Tyre and its pomp should be no more, belonging only to the past.