Divers trying to salvage what remains of the wreck of the Rena have had to swim through congealed milk fat floating on the sea.
However, relatively calm weather has allowed good progress to be made on the salvage operation this week.
Maritime New Zealand said containers lodged underwater on the starboard side of the wreck were proving very difficult to remove.
There have been 932 containers collected from the Rena of the 1368 on board when it ran aground on the Astrolabe Reef off Tauranga on October 5 last year. MNZ said the majority of the number 3 hold in the bow section had gone completely, with parts removed by gas cutting and the rest collapsing due to the swell.
Container recovery company Braemar Howells is finalising preparations for last phase of underwater container recovery plan – the lifting of several containers from the seabed.
The weather is expected to deteriorate over the weekend.