This is the ship that brings military troops and supplies from Oahu to Kawaihae Harbor en route to Pōhakuloa Training Area (PTA). I often see the ship going back and forth off the Big Island and had always assumed it to be a Navy vessel because, well, it’s a ship. But no, this is an Army LSV (Landing Ship, Vehicle) where they drop the ramp and roll the vehicles on or off.
These activities coexist with commercial shipping, pleasure craft, and locals enjoying the splendid beach and calm waters of the harbor, where I understand the snorkeling is pretty good. Got to try it out sometime soon.