Mr Jack pitched for the regional council to become a "funding partner" by committing between $3m and $5m to the project - which did not need to be provided up front.
The city council would be seeking government funding - with strong support indicated from both National, and Labour - and from the private and philanthropic sectors.
Regional councillors commended the city council on the "bold and ambitious" project, and the opportunities it offered the region, but Mr Jack faced a deluge of questions on the funding model and concerns over elements of the expansion.
Regional council chair Rex Graham said the project was "fantastic for our region, beyond anything else we've seen around the table", but worried about reaching the funding target.
"If you can leverage 20 [million dollars] off the Government that'll be an enormous help but $45m, it's a biggie for our region.
"We've got these big challenges. I love it [the project], but how are we going to do all these things with the budget we've got? That really worries me at the moment."
Mr Jack said he understood because Napier also had several big projects "on the go".
"But at the same time we recognise that this is a bit of a game changer for Hawke's Bay," he said. "This will be what brings people here, this will be a place that can actually start to change people's behaviours."
Having their partners on board, and government support, was an opportunity that needed to be taken advantage of, he said.
When asked if the regional council could be a corporate partner and receive revenue return from the aquarium, Mr Jack said: "[We] can always look at something."
He was also encouraged by councillor Debbie Hewitt to seek funding from Hawke's Bay's other authorities.
"One of my concerns is you're just focusing on the regional council when you know we have some huge challenges with our budgets going forward and our core competencies."
Given the regional council's jurisdiction they were the only Hawke's Bay authority the city council would be asking for funding from - other councils would be asked to provide support.
Mr Jack fielded other questions, including assuring the committee the process to get projections of the aquarium's visitor numbers and revenue was a "completely different" one to previous projects - such as the MTG Hawke's Bay and Art Deco buses - which had fallen short of expectations.
The previous council had led both those projects, and had not done business cases, or gone through analysis for them, Mr Jack said.
"This has gone through a completely robust process where we have brought in experts to determine figures. It's a completely different process."
Other development updates from the chief executive yesterday included that the aquarium's design be shaped from the start by Weta, local iwi and New Zealand's top marine scientists, or the possibility of the aquarium becoming part of a "Weta" trail for tourists, from Matamata's Hobbiton to Wellington's Te Papa.
