like shooting ducks in a barrel → περίπατος, παιχνιδάκι, παιγνιδάκι, πανεύκολο
as a duck takes to water, breeze, cakewalk, child's play, cinch, doddle, doss, duck soup, easy, easy as 123, easy as ABC, easy as cake, easy as falling off a log, easy as pie, easy as rolling off a log, easy peasy, easy peasy Japanesey, easy peasy lemon squeezy, easy pickings, easy street, easy-breezy, eath, effortless, facile, gimme, idiotproof, layup, light, like a duck takes to water, like falling off a log, like riding a bike, like shelling peas, like shooting fish in a barrel, like taking candy from a baby, natural, no-brainer, open and shut case, painless, picnic, piece of cake, piece of piss, simple, simple as kiss your hand, slam dunk, snap, trivial, troublefree, unchallenging, undemanding, undifficult, walk in the park, walkover