The stunning new seafront structure replaces a 1980s centre on the same site which was demolished in 2020 to make way for the new facility. Building began in January 2021, and the centre was handed over to the council's operating partner Freedom Leisure at the end of July.
Since then Freedom has been carrying out staff training and facility testing, helped by local sports groups and invited guests ahead of the initial public opening today.
Council leader Carl Smith said: "We set out to create a health and wellbeing centre fit for the twenty first century and that would help make the lives of our residents healthier and longer.
"Thanks to the fantastic work of our council officers, our construction partners, led by Morgan Sindall, and our advisers and funders including Sport England, New Anglia LEP, and the Norfolk business rates pool, I am confident we have done just that.
"From the start we have been determined that this should be a centre for everyone, whatever your level of confidence, and whether you live in the borough or are visiting us. Our learner pool and confidence gym are aimed at helping improve people's fitness in a supportive and welcoming way.
"We have made the centre as accessible as possible, including pool pods for those with limited mobility, and a Changing Places restroom.
"Anyone can come in and use the new café and enjoy its brilliant views of the beach and the sea, without paying any entrance fee, and there is free swimming for our residents aged over 75."
Freedom Leisure chief executive officer Ivan Horsfall Turner said: "The new Marina Centre is an excellent new health and wellbeing facility which offers a great range of activities. Freedom Leisure operate over 100 leisure and entertainment venues across England and Wales, and the Marina is one of the very best.
"We have a great team of people who can't wait to help the local community and visitors to Great Yarmouth enjoy the new facilities, and we are delighted to be working with Great Yarmouth Borough Council to help improve health and wellbeing in the borough."
A range of casual use and membership options are available, with local residents able to claim a Passport to Leisure discount card for a one-off fee of £15. Cardholders will be entitled to special offers, including free swimming for the over 75s and a 10% discount off a range of popular activities.
The centre's usual opening times will be 6.30am to 10pm weekdays, 8am to 6.30pm Saturdays and 8.15am to 8pm on Sundays, although individual activities may have separate timetables. There is extensive cycle parking on site, and a large pay and display car park with up to three hour's free parking for centre users.
The centre's opening will be further marked with a gala weekend over September 3 and 4, including a relay event featuring a specially-commissioned Marina Centre torch. The torch is based on a design by East Norfolk Sixth Form student Ednilson Dos Reis, whose artwork won a competition for local young people.
The new centre has been funded by Great Yarmouth Borough Council, plus £2.5m secured from the Government's Getting Building Fund via New Anglia Local Enterprise Partnership, £1.6m from Sport England, and £500,000 from the Norfolk business rates pool.