i could hear a lovely tailed maidens- a pun of siren most related to the doppler effect
amongst the waves- sound waves
she beckoned and splashed- shows the increasing frequency of the waves (like when you splash water it makes waves)
intense was her cry.- the high point or loudest of the siren
but i managed to pull aside- but as you pull away...
and slowly her calls faded away - her call grows quieter
you can usually observe it if you pass a ambulance/police/siren/constant noise or if you let them pass you