GIANT WAVES ON BEACH
Did you imagine a gigantic person standing on a beach waving, or a terrible storm with waves crashing on the beach?
Either would have been correct because the headline is ambiguous.
The reason is grammatical conversion - i.e the way one type of word can be read as another. The word giant can be read as either a noun (as in a gigantic person) or an adjective (describing the size of the waves).
Did you spot the possible meanings of the word waves?