The memorial is located in the Hudson River just west of Battery Park. Designed by sculptor Marison Escobar, it depicts four merchant seamen and their sinking vessel – the S.S. Muskogee – after being attacked by a German U-boat. The fourth man is in the water and is only visible when the tide is out. According to Wikipedia, the sculpture is based on a photo taken by the U-boat commander who attacked and sunk the S.S. Muskogee. All of the American crew died at sea.
This beautiful photo was taken by Raul Garcia Peñalver and found on Flickr.
The World War II Museum in New Orleans has recently opened the US Merchant Marine Gallery that helps tell the story of these mariners who crossed the Atlantic and Pacific transporting supplies, weapons and men to the warfront.