Studying the deep ocean requires many different types of equipment.  Scientists use the equipment to collect data, which they later analyze to find trends and develop hypotheses. Believe it or not, some of the equipment scientists use at sea isn't all that special -- Plastic tie wraps, burlap bags, plastic tupperware.  But, much of the equipment is highly specialized because accessing the deep is hard work: the tools have to withstand extreme conditions such as the corrosive salt water, extremely high pressure at depth, and temperatures that can go from icy cold bottom water to hot enough to melt lead (as is the case near some hydrothermal vents).