While the Greek army were blocking the advance of Persian forces through the mountain pass at Thermopylae, the naval forces of both were fighting at the straits of Artemisium.
When the Persians set sail for Artemisium they had around 1,200 ships, but many of these, about a third were lost in gales and storms at sea; however this fleet still greatly outnumbered the Greek fleet of around 280 ships.
On the 1st day of battle, the Persians attacked the Greek fleet hoping for a quick victory. The Greek ships formed a circle with their rams pointing outwards. They then sailed outwards towards the Persians vessels and rammed into them.
A quick victory was not to be had. The Persians fared badly with this Greek tactic and lost around 30 ships; sunk or captured.
During the night the Persians lost more ships as a gale had forced many of their fleet onto the rocky coast.
On the 2nd day, the Persians decided not to attack at all, but to concentrate on checking that their remaining vessels were seaworthy.
On the 3rd day, the Persian fleet attacked at full force. The battle raged all day and the Greeks struggled to protect the straits of Artemisium. There were many losses on both sides, however the Greeks could not afford to sustain those losses, they were still badly outnumbered.
The Greeks waited for news from the land battle at Thermopylae; they knew they could not hold Artemisium for another day.
When the news came, it was not good. The Greek army had been destroyed at Thermopylae and had retreated to the island of Salamis.
It was no longer of any use to protect the straits of Artemisium if Thermopylae was lost, so the remaining Greek ships retreated and also made their way to Salamis.