1 doll is found in the Rusty Cog, the first freighter near the bridge that leads to the anchor elevator. It is in the third (northernmost) section of the freighter, next to some crates on a ledge to the far right as the player enters through the hatchway on the lower level. This ledge can only be reached via a ladder in the second section that leads to the upper hatchway.
2 dolls are in Herbert's hut.
1 doll is in the stern of the small boat perched in the center of the canyon (where Herbert's tapes are initially before being scattered across the map), behind the cabin.