Sources : Sea-frog

Pliny the Elder [1st century CE] (Natural History, Book 9, 67): The sea-frog called the angler-fish [piscatrix] is equally cunning: it stirs up the mud and puts out the little horns that project under its eyes, drawing them back when little fishes frisk towards them till they come near enough for it to spring upon them. - [Rackham translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Fish 7.68): The frog of the sea [rana maris], which Pliny calls a 'piscatrix', pursues fish in this way: it has prominent horns under its eyes, with which it digs up and disturbs the mud to prey on them. Then the unsuspecting little fish, swimming into the disturbed mud and not seeing the predator hiding in it, swim toward it until they are close enough that they are suddenly torn apart by the enemy. Oh, how many of these, eager as they were for temporal gains, like troubled mud, were suddenly swallowed up and torn apart by the enemy of the human race! - [Badke translation/paraphrase]