Oecumenius — on Rev 8:8-9 (Commentary on Revelation)

“The divine apostle writes to the Romans, saying: "that creation was subjected to futility, not willingly but because of the one who subjected it, in hope that creation itself will be set free from the bondage of corruption into the freedom of the glory of the children of God." (Rom. 8:20-21) But when will it be freed? When there will be "new heavens and a new earth according to His promises," as Peter proclaims to us, writing in his second epistle. (2 Peter 3:13) In order for the earth, when it is renewed, to be freed from corruption and to become new, it is necessary that the sea also undergo this transformation; for the sea is within the earth. And how could it be purified itself, except through the cleansing of fire? Therefore, fire having fallen into it, it transformed the sea into blood, and killed a third of those within it. This, then, in relation to the letter and the perceptible, you might also conceive of as the sea, both by analogy and according to the laws of transformation, representing the present life because of the turmoil within it and the varied distractions; and fish and ships, symbolizing people immersed in the salty and bitter mud of sins, who, overwhelmed by sorrows, will ultimately fall into fruitless regrets over the lives they have lived.”