Acquire the new transducers, or blank ‘ducer “plugs" - then do a quick in-the-water changeout . It only takes a few seconds to pull the old transducer, then insert the new (matching) one. No need to cover the apeture (plunger) from outside.
Be prepared to be startled by a little geyser of inflowing water. You’ll take in a gallon of water, but no big deal.