The offshore shipowner said it now owns $81.9m or 11.7% of the $700m issue maturing in 2017.
The five-year debt pays interest of 1%.
In September and October it used $19.4m and $27m of its cash to acquire its 2017 bonds.
The company has also splashed $79.1m on buying its 3.5% 2014 series of convertible bonds in recent weeks.
