I am not aware of the existence of any legend about Bomere; but one or traditions are or were some years ago current respecting it. One is that it has no bottom. No end of waggon ropes have, it is said, been tied end to end with the view of ascertaining its depth, but in vain. Ergo, it has no bottom.
Another is that some two centuries ago, or less, a party of gentleman, including the squire, were fishing the pool, when an enormous pike was captured and hauled into the boat. Some discussion arose as to the girth of the fish, and a bet was made that he was bigger round than the squire, and that the sword-belt of the latter would not reach round the fish. To decide the bet, the squire unbuckled his belt, which was there and then, with some difficulty, fastened round the body of the fish. The scaly knight, for he no doubt felt himself to be one, being girt with the sword, began to feel impatience at being kept so long out of his native element, and, after divers struggles, he succeeded in eluding his captors, and regaining, at the same time, his freedom and his watery home. In later years he (so it is said) has been frequently seen basking in the shallow parts of the pool, with the sword still buckled round him, but he is too old a fish to be again caught. -- W.H.
The 'Magic' map shows an iron age settlement here at the edge of Bomere Pool, though no details are given yet. But it's interesting that folklore seems to know about this long-lost place. You can read the stories in Hope's 'Legendary Lore' on Feorag's site on holy wells (Hope is actually quoting Charlotte Burne's 1879 'Shropshire Folklore').
One story talks about a village full of heathens who didn't want their winter festival spoilt by a Christian priest nagging them - the village got completely flooded as comeupance. If you sail over the mere on Christmas eve at midnight though, you can here a church bell ringing.
Another story talks of a Roman soldier, similarly trying to make the ungrateful wicked locals repent. There's a love interest in this version, because the British governor's daughter is a good christian girl. At Easter Caer Caradoc apparently 'sent forth flames of fire' and the town was flooded. Unfortunately the soldier's betrothed didn't get spared, and when he rowed across the mere in search of her, he was drowned too. How very depressing.
The mere's bottomless by the way. And it contains a fish wearing a sword. No really. It's a bit of a complicated tale so I'll let you read that yourself.