Throughout the 1970s, the "Mary Rose" was meticulously surveyed, excavated and recorded with the latest methods within the field of maritime archaeology. Working in an underwater environment meant that principles of land-based archaeology did not always apply. Mechanical excavators, airlifts and suction dredges were used in the process of locating the wreck, but as soon as it began to be uncovered in earnest, more delicate techniques were employed. Many objects from the "Mary Rose" had been well preserved in form and shape, but many were quite delicate, requiring careful handling. Artefacts of all sizes were supported with soft packing material, such as old plastic ice cream containers, and some of the arrows that were "soft like cream cheese" had to be brought up in special styrofoam containers. The airlifts that sucked up clay, sand and dirt off-site or to the surface were still used, but with much greater precision since they could potentially disrupt the site. The many layers of sediment that had accumulated on the site could be used to date artefacts in which they were found, and had to be recorded properly. The various types of accretions and remnants of chemicals with artefacts were essential clues to objects that had long since broken down and disappeared, and needed to be treated with considerable care.