This was a flat bottom boat with no keel and very little freeboard and would have been totally unsafe in deep water with waves. A keel is a wing like surface that sticks straight down from the bottom of the boat running from front to back. The edge cuts through the water so it doesn't impede forward momentum but the broad flat plane surface causes tremendous drag on any force moving side to side and this is what keeps vessels from flipping over when waves hit them from the side. Freeboard is the amount of hull that rises above the water, and a low hulled boat without much freeboard can be swamped easily by waves.

With no keel and little freeboard a boat is very light, maneuverable, easy to row from, and can be brought right to shore in shallow water which are great advantages in streams and lakes, but taking one out in ocean waters is suicidally dangerous.

The Navy operated larger landing craft like the Higgins boat you see in movies for assaults from the ocean, and even these were unsafe except from very close in to shore.