Large crowds thronged the submarine tunnels of Underwater World Singapore (UWS) yesterday as the iconic oceanarium began the countdown to its closure on June 26, after 25 years and more than 30 million visitors.

With the school holidays in full swing and admission fees slashed to 1991 prices, it was difficult to negotiate one's way through the massive crowd of tourists and local families with children when The Straits Times visited yesterday.

Around 4,100 visitors admired the marine life there yesterday, nearly triple the average daily visitorship, said Haw Par Corporation, which runs UWS.

The slashed admission prices - from $29.90 to $9 for adults and from $20.60 to $5 for children - attracted businessman Harry Yeo, 43, who was visiting UWS for the first time with his wife and two sons.

Mr Yeo said: "I didn't visit last time because I thought it was too expensive."

Over the years, UWS has bred pink dolphins and about 15 species of fish and sharks.

It has also released critically endangered Hawksbill turtles and collaborated in a study of their migratory behaviour.

In recent years, though, UWS has been facing competition from the Marine Life Park and Universal Studios theme park, also on Sentosa.

On Monday, it announced it will close, as its lease expires in less than two years.

When Mr Ivan Goh, 45, heard the announcement of UWS' imminent closure, he knew he had to pay a visit to the aquarium.

"Twenty years ago, I came here ... and made a lot of good memories, so I wanted to bring my children here to make memories as well," said the salesman, who took his mother and three children along. "I'm sad that it's going to close."

His sentiments were shared by many Singaporean visitors.

Educator Soh Meng Le, 36, who was there with his wife and two young children, remembers UWS as a popular attraction of the past.

"Besides the bird park and the zoo, at that time, this (UWS) was the next biggest thing," he said.

Ms Tan Li Ying prefers UWS for its "child-friendliness".

"I feel that the fish seem closer and the viewing panels are the right height for my young children," said the 38-year-old mother, who thinks it is a pity the place has to close.

She also has childhood memories of the aquarium. "My dad would bring me (to UWS), and we would watch the pink dolphins."

Five pink dolphins, three fur seals and five otters have already been transferred to the Chimelong Ocean Kingdom in Zhuhai, China.

Haw Par said the transportation plan was co-developed by experts at UWS and the Zhuhai attraction, and that the animals have settled into their new homes.

Suitable destinations are being sought for the rest of the marine inhabitants.

UWS said it is holding a outplacement programme for its 70 staff to prepare them for future careers.

Mr Philip Chan, 62, who has been with UWS since the beginning and supervises the team of divers who care for the fish, feels sad that UWS is closing.

"Diving in the UWS tunnel is a special experience," he said.

"The animals have also grown familiar with us. The sharks, I think, can actually sense the presence of different divers.

"Every diver has a different breathing pattern and a different style of feeding."

He added: "Many ex-staff also told me that they'll want to visit and see the fishes one last time."