bond - This prophetic verse regarding a "great mountain", the "sea", "creatures that have life in the sea", etc., is merely reflecting the same type of terms found elsewhere in Revelation.
Sorry, but this is not the literal briny ocean being spoken of in this text. For one example, look at Revelation 12:12 where the devil and his angels have been cast out into the earth after Christ the Lamb and His blood have rid heaven of the devil's accusing presence for all time. "Woe to the INHABITERS of THE EARTH and of THE SEA! for the devil is come down unto you, having great wrath, because he knoweth that he hath but a short time."
The timing of this event is just after Christ's first ascension to heaven, when His blood offered on heaven's mercy seat in real time had legally annulled any accusations by Satan against the brethren. Consequently, Satan and his angels lost forever any further access to heaven, and were "thrown out of court", as it were, into the earth to do whatever damage he and his angels could do on earth for a SHORT TIME after the AD 33 ascension of Christ.
This attack of Satan and his devils would go against those who inhabited "the earth" (ge - the land of Israel), and also those who inhabited "the sea" (those living in Gentile nations in those days. Since God no longer puts this type of division on humanity between Jew and Gentile, this prophecy is one that took place before those divisions were erased - i.e., before Revelation 21:1 declares that there is "no more sea"). These inhabitants of the sea are HUMAN inhabitants - not aquatic life forms such as fish, sharks, dolphins, etc. The devil had no wrath against suchlike marine life forms, but he certainly DID have great wrath against humanity at that time (such as the I Peter 5:8 example about "the devil as a roaring lion walketh about, seeking whom he may devour").
If you want to see just one sample of the Gentile nations being compared to the sea, try this one in Isaiah 60:5. The context discusses the inclusion of Gentile believers among the children of Zion. "Then thou shalt see, and flow together, and thine heart shall fear and be enlarged; because the abundance of THE SEA shall be converted unto thee, the forces of THE GENTILES shall come unto thee". The parallelism in this verse equates the sea with the Gentile identity. So, "the sea" in question in Revelation 8:8-9 is referring to something in the GENTILE NATIONS being affected, not the literal ocean waves.
Next, the "great mountain burning with fire" was cast "as it were" (as if it were being cast) into the sea, with the result that 1/3 of this "sea" became blood. In this instance, scripture gives us permission to regard this "mountain burning with fire" as a literal geographical mountain. This "great mountain" I believe to be connected to the "7 heads" on the SEA Beast in Revelation 13:1. The other Scarlet Beast in Revelation 17:9 also has "7 heads" which are interpreted for us by John's angel as being literally 7 geographical MOUNTAINS that the harlot Babylon / Jerusalem is situated upon (the Mt. of Olives, Mt. Zion, etc.). The Sea Beast I believe represents the Roman empire of the pagan, Gentile world, with the 7 "heads" on this beast being another set of 7 literal, geographical mountains that Rome sat on, similar to the Scarlet Beast in the wilderness that had its own set of 7 literal mountains which Jerusalem sat upon.
So, if this "great mountain burning with fire" in Revelation 8:8 is connected with a literal mountain that actually is burning, I would say that this prophecy, given by John as he was writing in late AD 59 to early AD 60, was predicting the July AD 64 fire that devastated Rome, the capital city of the "Sea Beast" empire. To cast this burning mountain into the Gentile "sea" and to turn 1/3 of that "sea" into blood probably represents a 1/3 level of casualties in the capital city of Rome after that devastating AD 64 fire had burned for 6-7 days and demolished all but 4 of Rome's districts.
Next, in Revelation 8:9, it says that "...the third part of the creatures which were in the sea, and had life, died; and the third part of the ships were destroyed." The destroyed "ships" simply represented the 1/3 drop in commercial trade taking place in Rome immediately after this AD 64 fire that leveled much of the city. The Annals of Tacitus tell us that grain and the necessities of life had to be shipped in from Ostia and neighboring municipalities after the fire, to supply Rome's needs while it started its rebuilding program.
As for the "CREATURES which were in the sea and had life" dying after this event, this represented the saints who lived in Rome and other Gentile nations who were martyred in the subsequent Neronian persecution that pinned the blame on Christians for starting the July AD 64 fire at Rome. The word "creatures" does not necessarily have to be referring to marine life forms here. It can also refer to humanity, since we are told that "...if any man be in Christ he is a NEW CREATURE..." The Greek word is based on "ktisis" in both verses of Revelation 8:9 and II Corinthians 5:17.
So, these "creatures" in the sea who had life and then died were meant to represent those saints who possessed eternal life and who were martyred during those 3 1/2 years of persecution launched by Nero, lasting from late AD 64 until mid AD 68, which was when Nero died. This Neronian persecution period was of such a notorious nature and extent that it is entirely plausible that a 1/3 total of the Christians dying in Gentile lands, particularly in Rome, could be attributed to this Revelation 8:8-9 prophecy.
The book of I Peter, written around AD 65, (just after the AD 64 fire at Rome), mentions this "fiery trial which is taking place" for those he was writing to (i.e.,"the elect sojourners of the dispersion of Pontus, of Galatia, of Cappadocia, of Asia, and Bithynia") under "various trials" (I Peter 1:6) that were compared to being "tried with fire" (I Peter 1:7).
In addition, this 3 1/2 years of Nero's persecution of the Christians between late AD 64 and mid AD 68 was the prophetic fulfillment of the "little horn" on the dreadful 4th beast in Daniel 7:8, who would "wear out the saints". These same saints in Daniel 7:25 were to be "given into his hand until a time, and times, and the dividing of time" (the 3 1/2 years following the AD 64 fire at Rome). Since Daniel 7:24 (LXX) says that this "little horn" would "exceed all the former ones in wickedness", this describes Nero's character and actions toward the Christians exactly, compared to the other ten emperor horns on this 4th beast.
God had a distinct purpose for allowing 1/3 of His saints to be martyred during those years of persecution initiated by Nero: it maximized the total number of saints who would be able to participate in the bodily resurrection of AD 70, which fell on Pentecost day (the 1335th day of Daniel 12:12, which particular day I have written about in reply #19 to the post "The paradigm for....the Three Resurrections").
I'm afraid that the OP mention of present-day radiation poisoning levels in the ocean, which may well be true, has no bearing on the prophecy of Revelation 8:8. This particular prophecy was included among all the prophecies that Revelation 22:10 said were "AT HAND" and unsealed in the days John was writing.
Therefore, this Revelation 8:8 prophecy is long past, and presents no threat to us today.