You once again go through the temple of the Ocean King. Once you get to the part where you put the three stones on there pedestal, place them in this order square, circle, and then triangle.Then go into the room and go back out the floor will have sunk.
Yes,you can find items on mercay island for phantom hourglass,in the temple of the ocean king.You can find the the southwestern sea chart (no requirements),the phantom hourglass,the northwestern sea chart (after you beat the temple of fire for both),the southeastern sea chart and the northeastern sea chart (after you beat the ghost ship for both).
you go to the northeaster sea. Goron island is your first stop when you get there.
does zauz have the information about the 4th sea chart on the legend of Zelda phantom hourglass
The 4rth sea chart
southeast
Get the 4th. (do what the skeleton says to do)
THE LAST SEA CHART IS IN THE OCEANS KING TEMPLE. (you only get the sea chart the 5th time you are sent there)
that's the last sea chart that you get in the temple of the ocean king.
the fourth
Four. The Northwestern, the Southwestern, the Northeastern, and the Southeastern.
the 3rd sea chart is located in the deepest part of the temple on Mercay island
If you are refering to the three pure metals used to make the phantom sword, then you will need to go down into the Temple of the Ocean King and search for the last two sea charts. The southeastern is easy to find, but the northeastern is a little tricky to find. You can refer to other questions on how to find the northeastern sea chart.