The ad on Gumtree offers a double room overlooking Queen's Park in Brighton for absolutely no rent.
The drawback is whoever takes the room must dress like a walrus, and act like one, for two hours a day.
The odd demand comes from the anonymous poster of the advert, who explains they had spent three years living alone on St Lawrence island with their only friend being a walrus whom they named Gregory.
The ad reads: "Never have I had such a fulfilling friendship with anyone, human or otherwise, and upon leaving the island I was heartbroken for months.
The poster said they had constructed a realistic walrus costume which "should fit most people of average proportions, and allow for full and easy movement in character."
For about two hours a day the lodger would have to wear the costume and "be a walrus", including making walrus noises and eating fish.
The advert was put online yesterday and already has gone viral on social media sites.
It is unknown if the post is a hoax or the poster genuinely misses their walrus friend Gregory.
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