Suggestions from locals, many of whom have visited the Aquarium in the cliff face next to La Vallette bathing pools in St Peter Port, include use as a gym, a cocktail bar and a crustacean breeding centre.
The States are seeking expressions of interest for the premises.
Fiona Le Page said the site had many advantages, including a great view that would appeal to many.
‘It’s a great building,’ she said.
‘It’d be a shame not to see it used to its advantage – perhaps for a change, it could be used as a gym or fitness centre.
‘Parking would be an issue, but I’m not sure how anybody who takes it on would get around that. The parking is full along here now and it’s closed.
‘The previous owners spent a lot of money on making it nice, but if it doesn’t have the footfall then it won’t work.’
The tunnels opened as the Guernsey Aquarium in 1967 and were recently refurbished and renamed The Aquarium in 2017.
It was the world’s only tunnel aquarium and provided a unique experience for visitors.
Sarah Barnes said this is something that could be used to its advantage.
‘I reckon a nice cocktail bar would be a great addition,’ she said.
‘It’d be a great setting, a little far away from the rest of the Town, though its uniqueness would be a big draw.’
Another idea from former Herm Island tenant Adrian Heyworth and wife Penny was to develop the tunnels into a breeding centre.
‘It’s a real shame to see it closed because it’s a good facility,’ Mr Heyworth said.
Mrs Heyworth said they used to take their grandchildren to the attraction.
‘I’m sorry the public didn’t keep it going,’ she said.
‘Perhaps the tunnels could be used as a lobster breeding centre or the like, somewhere to further the island’s marine wildlife.’
The original tunnel dates from 1864.
Then during the Second World War, occupying Nazi forces used slave labour to expand the tunnels and stored military vehicles and ammunition in them.
In 1967, the tunnels were transformed into a specialist aquarium with more than 40 tanks.
A number of changes have been made to the site in order to attract more visitors. However, due to lack of tourism and a lack of support, after 52 years as an aquarium, the doors closed for the last time in October.