The event at the award-winning aquarium on Thursday was only the second time the entire attraction had been closed to the public for a wedding since it was granted a licence to host them in 2006, although the previous occasion was to allow guests to get away on time.
Staff signed a confidentiality agreement to prevent details coming out, but a wedding car was seen leaving and it is thought a pop star from the 1980s was in attendance.
Members of the public, some of whom had travelled from South Yorkshire, were told the attraction was closed for a private function and were given free tickets.
Colin Brown, chief executive of The Deep, said: “The people that wanted to come in, most of them cam in and we put activities on for them in the education room and made the cafe available, and when the event was over we gave them free tickets.
“I haven’t signed a confidentiality agreement but I asked my staff to sign confidentiality agreements because I feel the people wanted it kept confidential for a while and we will honour the bride’s wishes.”
He added: “We wouldn’t have closed for it had it been any other time of the year but the request came in on one of our quietest times of the year - we wouldn’t have considered it between February and August.”
The Deep, which opened in 2001, hosts about 20 weddings a year and can be hired for private parties.