Ballast that added 30 per cent to the weight of the Lamma IV made the vessel "sink like the Titanic" after its collision with the ferry Sea Smooth, an inquiry into the National Day sea tragedy heard yesterday. Naval architect Dr Neville Armstrong also criticised storage of the boat's life jackets, which he said resembled "somebody's lunch". Armstrong, a commission-appointed expert, said the 8.25 tonnes of lead and seven tonnes of unspecified material were installed in the stern of the Lamma IV in 1998 to stabilise it. But it substantially reduced the efficiency of the Hongkong Electric boat's sub-division - the segregation of hull compartments that enabled the vessel to remain afloat when damaged. "It was not recognised at the time that the watertight subdivision had been compromised by the addition of weight," Armstrong said. When the boat was built in 1995, it had "excellent" sub-division that would have allowed it to remain afloat when any two compartments were flooded. But when it was damaged in the collision off Lamma on October 1 last year, it sank very much like the Titanic did in 1912 - upright by the stern without tipping to either side. Armstrong said earlier that the need for watertight partitions in ships was first recognised after the sinking of the Titanic that led to 1,502 deaths. Returning to deliver the second part of his expert report on maritime safety, he outlined 59 suggestions. He said the number of children's life jackets stipulated in 2008 legislation - 5 per cent of the total number permitted on board - was not enough. The number should be at least 10 per cent, according to the International Convention for the Safety of Life at Sea. He also said the standard of life jackets should be outlined in law, and that infant life vests were needed as well. The way life jackets were stored on the Lamma IV - tied up in plastic bags like "somebody's lunch" - also surprised Armstrong. Captain Nigel Pryke, another marine expert, proposed that investigation and prosecution units be separated from the Marine Department, as international practice recommended those be independent from any party involved in marine accidents. Noting that only four coxswains were fined HK$1,000 to HK$15,000 in 11 recent high-speed collisions, Pryke said investigations should go beyond looking at an individual. The commission also found light wires on the Lamma IV were cut by the department for its investigation. The inquiry into the collision and sinking with the loss of 39 lives continues today.