What Sea Lies 400 Miles West of Darwin? None—Timor Sea Is Much Farther

There is no sea 400 miles (640 km) west of Darwin, Northern Territory.

At that distance west of Darwin, you are still over land—specifically, the Northern Territory's western Top End or the Kimberley region of Western Australia. The coastline at that latitude (approx. 12°–14°S) runs roughly northeast-southwest.

Actual Distances to Water Bodies

• Timor Sea: Begins ~1,000 km (620 mi) west/northwest of Darwin, off the Kimberley coast
• Joseph Bonaparte Gulf: ~400 km (250 mi) west-southwest (closest saltwater)
• Beagle Gulf / Van Diemen Gulf: North/northeast of Darwin (Darwin sits on Beagle Gulf)
• Arafura Sea: Northeast, beyond Van Diemen Gulf

Why the Confusion?

Darwin is a coastal city on the Beagle Gulf (part of the Timor Sea system). The Timor Sea itself is much farther west. The 400-mile figure may confuse the distance to the Western Australia border (~450 km west) with the Timor Sea coastline.

Bottom line: 400 miles west of Darwin is inland Western Australia, not a sea.