Rainwater rhymes with:
backwater, breakwater, bridgewater, bywater, clearwater, coldwater, deepwater, drinkwater, fitswater, fitzwater, floodwater, freshwater, goldwater, headwater, pinkwater, sidewater, stillwater, tidewater, underwater, wastewater, whitewater
Rainwater sounds like:
rander, reenter, reentry, reindeer, remainder, reminder, render, renter, renteria, rinderer, rounder, roundtree, rountree, rowntree