Where to find them: Arm yourself with a deep-sea fishing pole (you can craft with carpentry skill with 50 stems, 50 mytheril ingots, 5 exp, 20 diamonds) and lots of shiny baits (craft always with carpentry: 5 blood rock bars, 5 skins, 2 old copper ingots, 2 copper ingots, 1 diamond), take a boat and go in the middle of the sea, they will pull up lots of fish (remember that with the fish cut and then cut into slices you make oil) and bottles. Inside the bottles there are always maps if they don't break when you try to open them.

Once you have the map, to decipher it you need to have the magnifying glasses in your backpack (you can created with Carpentry) and the sextant you find even by a handyman. A map will open indicating where to find the treasure (you can help yourself with the maps published on the site). Once you are near the treasure you can click on the lenses and then on the map and an inscription will appear showing directions on where to go .. type: it is located to the north-west
When the inscription "the point seems to be very close" appears, start digging with the shovel (with high mining you will find the treasure more easily), if the writing appears:
"excavated and dug but it seems that no treasure is here" ... it means that you are really close
"digging and digging but can't find anything" ... means that you are some tiles away