Saltchuk Resources’ $950m deal to buy Overseas Shipholding Group is seen as a diversification move that adds a new fiefdom to the US maritime conglomerate’s growing empire.

The Seattle company already has a wide portfolio in domestic and regional shipping, including container and ro-ro vessels, tug and offshore service vessels, and a fuel and lubricants business.

But Tampa-based OSG offers it something it does not have: the largest fleet of tankers and articulated tug barges (ATBs) operating in the booming market protected by the US Jones Act.