It was collected by Department of Conservation and Auckland Museum staff before being given to the University of Waikato to conduct their research.
Toby Reynolds, 6, and Jack Reynolds, 3, took turns sitting on their dad, James Reynolds' shoulders.
"I saw the shark's head, it was cool," Toby said.
"It's a good community event that is really family focused," mum Rebecca Reynolds said.
Reuben Bopf, 9, and brother Owen Bopf, 7, were enjoying looking through microscopes at seagrasses but had an obvious favourite part of the fun day.
"I like the shark dissection. I do like seeing stuff cut open," Reuben said.
There was no sign of rainy autumn weather as families applied sunscreen and sun hats were out in full force.
Harry Singh, Bay of Plenty Regional Council communications adviser, said the turnout had exceeded the council's expectations.
"It's a great opportunity for us to show the community what it is we do, in a fun way," Singh said.
He said it was important to get kids involved and learning about the marine life that lived in Tauranga Harbour.
There was a range of activities on offer including flax weaving, crab and critter hunts and colouring stations.
Sarah Omundsen, Bay of Plenty Regional Council Tauranga catchments manager, said the aim of the fun day was to help the public better understand Tauranga moana.
"We used to have a harbour symposium but we've changed the format to make it more engaging and fun," Omundsen said.
"We wanted to create a family-friendly event so our community can learn about their harbour as well as the work that's going into looking after it."