A major shareholder of US-listed boxship owner Seaspan has revealed details of a big stock sale.

Companies controlled by the Washington family have registered up to 52.81m shares for sale at a maximum price of $8.98 each, against a closing price of $9.16 last Friday.

This would bring in more than $474m.

The shares are owned by companies including Deep Water Holdings, the Kevin Lee Washington 2014 Trust, the Kyle Roy Washington 2014 Trust and the Kyle Roy Washington 2005 Trust.

Billionaire Dennis Washington has long been a significant shareholder in Seaspan, which was co-founded by his son Kyle.

The move follows increasing investment from Fairfax Financial Holdings, which now has 36% in the company.

It owns 76.9m shares after closing the second tranche of its $1bn investment last week, when it bought $250m of senior notes and warrants which were immediately exercised to double the proceeds.

The additional capital is earmarked for growth and debt repayment, Seaspan told investors.

An SEC filing by Seaspan appeared to indicate that Fairfax had a stake of 47.7%, but Seaspan explained that this includes 25 million unexercised seven-year warrants.