Danaos Corp chief executive John Coustas and his family have dropped another $25m into the boxship owner, bringing their stake in the company to well over a third.

Danaos Investment Limited as trustee of the 883 Trust purchased 305,118 more common units of Athens-based Danaos, according to a regulatory filing.

The shares fell 1.89% to $81.57 within 45 minutes of Friday's open trading on the Nasdaq stock exchange in New York, thus taking the value of the family's latest investment to $24.9m.

Danaos Investment now owns 39% of Danaos, up from 31.2% held since December 2019, the filing showed.

Danaos is enjoying a booming boxship market that has pushed its total charter backlog up until 2026 beyond the $2bn mark.

The company, which plans to grow to 77 boxships by October, on 3 August reported net profit of $670m for the first half of 2021, up from $67.6m in the same period of last year.

Coustas has said the company plans to increase the $0.50 quarterly dividend it paid out in the first two quarters of this year at some point next year.

Danaos shares, which trade under the ticker symbol DAC, have skyrocketed this year from $21.76 on 4 January as a result of a boxship sector that has seen incredible demand this year.

The unprecedented squeeze in capacity, which has also propelled boxship charter rates to record levels, began in early 2021 when the sector faced a "Covid crunch" of demand for container transport.

This extreme pressure, which has prompted owners to expand their fleets, has continued amid strong US consumer demand for imported goods.