Specialist vessels designed for towing and/or anchor handling. Predominantly employed in the movement of rigs and platforms, and for the handling and laying of their anchors. Anchor Handling Tug Supply (AHTS) vessels combine the role of supply vessels and anchor handling tugs. They are the backbone of offshore operations and constitute the largest proportion of offshore vessels. Not only do they deliver supplies such as deck cargo, water, fuel, dry bulk and mud to oil rigs and platforms, they are specially designed to provide anchor handling services, towage duties and in some cases also serve as an Emergency Towing Rescue and Recovery Vessel (ETRRV). Some modern AHTS vessels are also equipped for fire fighting, rescue operations and oil recovery to enable them to have a more multi-role capability.
Since the AHTS provide a multi-utility facility, as naval vessels they are demanded in a higher coverage area. Also since in contemporary times, oil drilling from the oceanic areas has increased and is a regular activity, the increase in demand and usage of AHTS makes a lot of relevance and sense.
Anchor handling vessels are designed with high horsepower to tow drilling units and perform anchor handling operations as well as the ability to carry supplies to platforms. The increase in deep water exploration has led to higher horsepower vessels to handle the heavier gear required to operate at such depths. In the offshore service vessel fleet, new deep-draft, very large, high-horsepower anchor handling/tug /supply vessels have evolved to move these large new sophisticated drilling rigs, handle their anchors, chain and mooring lines, and meet all kinds of service demands of the new generation of deepwater rigs and production platforms.