The first thing is to ensure we have an accurate translation. The subject is the "Temple Tax" rather than "Tribute" - which is how the KJV translates this. The Temple tax was instituted in Exodus (Ex. 30:11-16). Tribute, on the other hand, is what a vassal pays each year to the king. The Roman Caesars minted "tribute" coins. If you pay tribute to Caesar, you acknowledge his "kingship" in your life. That is the debate in Mark 12
The "tribute" was paid in a denarius and had an image of Caesar on it. The inscription said:
"Tiberius Caesars, son of the Divine Augustus, Emperor"
and the obverse declared Tiberius
so this was considered worshiping a false god in the eyes of the Jews.
Point 1: The Temple tax was paid using a Tyrian Shekel. A problem with the Tyrian Shekel was that it had a pagan god on it - Melqarth-Herakles (Hercules in the Roman pantheon). Tyrian Shekels had high purity silver content and were, therefore, the only coins authorized by the religious leaders to pay your temple tax. It also appears that when the Tyrian mint closed - they moved the minting operation to Jerusalem - and continued to mint the Tyrian Shekel with the Tyrian god on it.
As Gordon Franz notes:
"The rabbis decided that the commandment to give the half-shekel Temple tax, with its proper weight and purity, was more important than the prohibition of who or what image was on the coin."
Point 2: The "sea" in the ancient Near East (Old Testament as well as New) was an image of judgment.
Dane Ortlund writes in his journal article What Does It Mean to Cast A Mountain into the Sea? Another Look at Mark 11:23 in Bulletin for Biblical Research:
The “sea” likewise has a consistent meaning in the Bible beyond the mere
referent to a large body of saltwater. Throughout the Bible, the sea often
symbolizes darkness, separation from God, divine judgment
So a possible interpretation is that Jesus is making a statement about the fact that the temple authorities were using a coin that violated the command of no graven image to pay for the functioning of the temple. That the coin is "in the sea" - the place of divine judgment - would be a symbolic way of showing what you think about the coin approved for use in the temple.
A significant portion of the message of the Gospels - particularly Mark - is that God's judgment is coming to the Temple and the religious leaders. Following the words of Malachi 3:
Then suddenly the Lord you are seeking will come to his temple (Mal. 3:1)
So I will come to put you on trial (Mal. 3:5)
Jesus is continually obedient to God's commands. He pays the tax. But does it in a symbolic manner to show what he thinks about the coin and the hypocrisy of the temple authorities.