The sinking position of 0°30’N, 38°45’W placed the raft just north of the equator and well east of the Brazilian coast. The rescue position near Salinópolis, in the state of Pará, is at approximately 0°36’S, 47°35’W — just south of the equator and significantly further west, consistent with the westward drift of the South Equatorial Current followed by a southward drift along the coastal shelf as the raft approached the Brazilian coast.
The approximately 750-mile westward drift over 133 days works out to an average daily drift rate of roughly 5.6 miles — entirely consistent with the South Equatorial Current, which moves at speeds of roughly 0.5 to 2 knots (0.6 to 2.3 miles per hour) in this region, depending on wind conditions and seasonal variation. The raft was not traveling in a straight line; it was responding to the daily variations in wind and current that characterize the equatorial zone. But the dominant direction of motion, over the full period, was westward toward Brazil.
The color change that Poon Lim reportedly observed — the transition from the deep blue of the open ocean to the lighter, greener hue of coastal water — is a well-documented navigational indicator with a specific scientific explanation in the region he was approaching. The Amazon River discharges approximately 209,000 cubic meters of fresh water per second into the Atlantic, along with a substantial sediment load. This discharge alters the optical properties of the ocean surface water over a remarkably wide area — the distinct plume of the Amazon’s fresh water can be detected hundreds of miles from the river’s mouth, creating the transition from deep-ocean blue to the turbid green-brown of river-influenced coastal water that Poon Lim appears to have noticed.