J. W. Westcott II is a post office boat that delivers mail to ships while they are underway.

[3] Any mail addressed to members of ships' crews on vessels transiting the Detroit River can be delivered to them via J. W. Westcott II by being addressed "Vessel Name, Marine Post Office, Detroit, Michigan, 48222."

[2] The mail is delivered to the appropriate ships (mainly lake freighters) as they transit the Detroit River, utilizing ropes and buckets.

[2] On 23 October 2001, J. W. Westcott II sank in the deep water under the Ambassador Bridge while caught in the wake of Norwegian oil tanker MT Sidsel Knutsen.

The captain and one other crew member were killed; the two passengers, both pilots, were rescued.