Casual bombing costs $8 to $10 for five jumps and day passes are also available. The platform is multiple levels, up to 10m high.
Laity said people were welcome to swim in the lake as usual too.
The largest prize in the competition is $2000 for the open male division. Another $3000 cash and other prizes are available across the seven divisions.
On Sunday, finals are from 3pm to 5pm.
Laity said the organisers weren't entirely sure how many people to expect but guessed 3000-4000 daily.
"The event is so unique and it captures a lot of people.
"As Kiwis we're surrounded by water … I think, at the end of the day, people love to swim."
He said security guards and police would be present at the event, which was alcohol and drug free.
Bombing will be open from 10am to 6pm daily and 11am to 4pm on Waitangi Day. Buy a casual pass on the day or enter the competition at nzbombcomp.co.nz.
Bombers will be judged on the splash height and volume, style and originality.
Flochella will take place on Monday before Waitangi Day.
This is the first time the music festival is in Rotorua after being at Lake Taupo in previous years.
Event manager Kat Hicks said more than 5000 tickets had been sold and were still available.
"It's a one of a kind event in an amazing venue and there's a great line-up."
Despite being on a normal working day, Hicks said organisers were expecting lots of people to take the day off.
The event is family friendly and is drug and alcohol free.
Police will be there and will help with crowd control and traffic management.
There will also be security teams checking no one brings alcohol into the venue.
Over the weekend there will be very limited parking at the lake. Parking will be $25 cash. Attendees are being encouraged to use the bus which costs $2 return and runs back and forth all day from 9am.
Jupiter Project will also be playing at an after party at Lava Bar from 8pm. Entry is free with a Flochella wristband or there will be a cost without.
Flochella
When: Monday, 11am-6pm Where: Tikitapu (Blue Lake)
Tickets: $45 from grabone.co.nz
Buses: $2 return from 9am from Puarenga Park
Boats: To watch from a boat a pass is required. The boat ramp will be closed to others
Line up: Amy Shark, Kings, Mitch James, Drax Project and Jupiter Project
NZ Bomb Comp
When: Saturday and Sunday
Register at www.nzbombcomp.co.nz
