波は岩にぶつかってくだけている。

wave

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

rock; boulder; crag; cliff; anchor

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to strike against; to collide with; to bump into; to conflict; to encounter; to meet; to clash

to break (into pieces); to be broken; to be smashed; to collapse; to crumble; to decline; to cool (e.g. enthusiasm); to dampen (e.g. one's will to fight); to become less formal; to throw off reserve; to become affable; to become easy to understand (e.g. a story); to be worried