If u are talking about Phantom Hourglass. All of the sea charts can be found in temple of the ocean king. They are on different levels ad the final one is on the last level. U will need to get all the fairies and do specail triggers to get lower and lower.
In the Northeaster sea.
After getting the Spirit of Courage, the next thing to do is go to the Temple of the Ocean King and get the next map.
in the south western sea, in the top right corner of the map
There are multiple sea monsters. Please specify which sea monster in a separate question next time.
Its at the bottom of the sea in the south east map. it took me a while to find.
if you meaqn by sea chart then all of them are in the ocean temple you can not obtain them all at once.
One square directly below Dragon Roost Island
You have to go to the ocean temple and get the next sea chart.
find the sea chart that matches the other sea chart upside down and close the ds. and it will be transferred on your map.
in the northeastern sea next to the isle of gust
the next zelda is on wii u which is called legend of zelda :wii u
check the map at telmas bar. it will mark his location on ur map.