Well, i found somewhere a list with all possible chest drops.
This list refers to a Sea Caves Regular Chest, a Sea Caves Good Chest and Marten's Chest. Searching the Sea caves Area, i managed to find only the Sea caves Regular Chest (it is the one with the hook and line beside it) and Marten's Chest (near Marten's Tomb, containing Rennaissance Lute and Hunter's Bow.
However, i did not manage to find a third chest in the sea caves area. I am sure i'll have to search the whole area again, and i've already searched this forum. The only reference for a third chest is one of Kiwi's, saying in two different occasions that there is a chest in Sea caves, generating a ghost every time you open or close the chest.
Since i did not find such a chest (have found the above two only), my conclusion is that Kiwi's Chest is the chest i'm searching for (except if his information is not true).
I would be very much obliged if someone gave me directions to this 3rd chest in the Sea Caves area. I pretty much want to find it, because i need a gem of power for my Gnome Lord, and have already opened every other chest i could get it (for example, Rapax king's Chest, or Hoarder slime in a retro dungeon)
Thanx for the help
1) When you arrive at Sea Caves, head to the right, follow the beach, get the hollow tube then turn around and enter a cave. Keep to the left, fight the crabs, get the hook&line next to the chest.2) Climb the rope, fight the Death Lord, take the north tunnel, fight two ghosts, open the chest.
3) Get the spiked boots, put on the spiked boots. Keep to the left and enter a slippery patch. Keep Extremely To The Left Don't Fall Down The Hole. Open the chest behind the hole.