Divers working on the wreck of the tugboat that sank with 18 Ukrainian seamen on board will try to get into the vessel after locating an entrance near the deck, a senior fire officer said yesterday.
But the work is difficult because of hostile conditions underwater, and it could be days before the supply boat can be lifted from the seabed.
Chief fire officer Chow Wing-tak said the divers had reached a crane on the right side of the deck which, according to a layout plan obtained on Monday night, was just 10 metres from a cabin door.
'There is no way to estimate how long it will take [to get in], but we will bring up the crew members dead or alive,' Mr Chow told an RTHK programme.
Fire Services Department divers have made at least 20 unsuccessful attempts to enter the hull since the tug sank in a collision with a mainland freighter on Saturday.
'The divers can only get close to the entrance when the tide is turning - the only time that the current is weaker,' Mr Chow said.
He said underwater visibility was as poor as half a metre, meaning direct contact by divers was the only way to check the hull of the 80-metre vessel.
Steve Chan, a diving course director with Pro-Dive Hong Kong, said divers could 'fly like a kite' if they lost hold of their ropes in such a strong underwater current.
The location of the collision site also added difficulties to the rescue operation, he added.
'The water discharged from the Pearl River Delta carries a lot of mud, and the sunken ship appears to be settled in a trench more than 30 metres deep,' he said.
The diving coach, with 25 years of experience, said the period for rescue had passed and it was time to recover the wreck.
The Guangzhou Salvage Bureau has already deployed one floating derrick at the site to help recover the tug but another, the Hua Tian Long - the biggest derrick of its kind in Asia - is expected to join it by Friday.
'Hua Tian Long is the most capable derrick to help in this situation but it does not stand by for rescue and we cannot expect it to come immediately,' said Mr Chan, who had worked with the bureau in the recovery of the wrecked Song dynasty vessel Nanhai No 1 last year.
Lo Kok-keung, of the department of mechanical engineering at Polytechnic University, said the sunken ship could be raised when the second derrick arrived.
'It is not possible to empty the water out of the supply boat under the water. It has to be righted for the water to be pumped out and then towed to shallower water.'
Dr Lo said the time taken for the operation would depend on traffic in the channel.
The Ukrainian-registered supply tugboat Neftegaz-67 sank after drifting 400 metres from where it collided with the inbound mainland-registered freighter Yaohai near The Brothers islands.
Initial attempts to tow the wreck free failed as the ship's mast had sunk into the mud.
The Hua Tian Long, Asia's biggest floating derrick, will be tasked with the salvaging of the Neftegaz-67. Here's how it measures up
Weight: 40,792 tonnes
Length: 167 metres
Width: 48 metres
Lift power: 4,000 tonnes
Maximum operating depth: 300 metres
Sources: China Daily, gz-salvage.com.cn