Starfruit,
I think it's not Punggol Park, it's Punggol Marina?
We went Bishan Park last night. $15 for 1 hr, $25 for 2 and $30 for 3 hrs, per rod.
This one at Bishan Park is quite good cos they have many prawn ponds, can move around. They have free BBQ pits for you to BBQ the prawns after that too. They sell those hawker food there as well, like chicken wings, satay, beehoon, western food & etc ... Can eat while prawning. They have a branch at Jurong as well, near to Jurong Birdpark, I think.