A nondescript square building that has room for two guards that change shift every 8 hours.  There's a fireplace inside, food enough for a week and a large earthenware jug of water for cooking and drinking.
Guard Shack, Outside Tower
guard
bivalve
I am a bivalve that lives in water.  I have a shell that protects me.  I sometimes can carry a pearl inside my shell. My shape is oval and irregular.
This here is my home! I am a bivalve keeping my peace... Your home!? Don't make me laugh. Isn't your home the sea?  I live wherever there is water!  This jug of water is for cooking, silly mollusk. If you jump in there you will surely meet your end roasted over the fireplace. Of course you would consider me for food! When I hold more valuables than food.... You hold something more valuable than food? Tell me what you have and I may spare you yet. You seem to know so much about me but do not know what I contain? Tell me what you contain before I call the other guards! I don't like small talk.  I only sometimes carry a pearl, silly guard. A pearl you say? That will make an excellent prize for my king!  I will give it to you IF AND ONLY IF you make me a water pond in this shack here so I can stay. Seeing as you are a defenseless bivalve and I am a guard with a sharp knife, I see no reason why I shouldn't just take it from you.