With the exponential increase in offshore oil and gas exploration and development in the past thirty years a whole new category of ships has developed. Generally called offshore support vessels, they are divided in many sub-categories.
Some are purely cargo vessels, aimed at getting supplies out to rigs at sea. Some are multi-purposes, able to do a variety of chores depending on the need.
One such is Maersk Challenger, built in 1986 and classed as an anchor handling tug supply vessel. Sort of a jack of all trades, its large deck area allows it to carry significant quantities of cargo in containers on deck. It is also fitted with tanks to carry fuel, potable water, drilling mud, cement and other bulk commodities needed for drilling and production.
However when the need is there it is a powerful towing vessel, rated at 160 to 173 tonnes bollard pull. This translates into about 14,000 horsepower which can be brought on line when needed. If the ship is performing less onerous duties it can operate without full propulsion.
Maersk is one of the largest offshore operators in the world, with more than 60 vessels. Its Canadian operation is a significant one with 10 ships and an 11th to be delivered this spring. It is therefore the largest Canadian operator of offshore support vessels. (Some would call them boats.)
And yes some are certainly tugs, but only on a part time basis. Maersk Challenger is seen leaving Halifax this morning with a deck cargo.