rising tide has 2 distinct synonyms spread across 1 of its 1 sense. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the occurrence of incoming water (between a low tide and the following high tide)
“a tide in the affairs of men which, taken at the flood, leads on to fortune”
Synonyms, antonyms and the broader and narrower relations for rising tide come from Princeton University’s WordNet. Full sources and licences.