Sea monster
Sea monsters are the following monsters living in water:
The eels and kraken can pull you into the water, which can drown you very quickly, unless you have magical breathing, or are wearing a noncursed greased cloak or an oilskin cloak, in which case they cannot grab you.
If you are being pulled underwater by a sea monster and you do not trust that you can kill it fast enough, you may rely on some escape item. Additionally, if you are levitating controlledly over dry land when the monster grabs you, stop levitating and the monster will become startled, releasing you.[1]
Some people use the NetHack options file to replace the ; character with another, more readable one (such as 7) as a way to better distinguish a dangerous class of monsters from the water symbol.
