This Amendment No. 6 to Schedule 13D ("Amendment No. 6") relates to the Common Stock, par value $0.01 per share, of Ultrapetrol (Bahamas) Limited, a Bahamas corporation (the "Issuer"), which has its principal executive office at Ocean Centre, Montagu Foreshore, East Bay St., Nassau, Bahamas, P.O. Box SS-19084.  This Amendment No. 6 amends and supplements, as set forth below, the Schedule 13D filed by the Reporting Persons with respect to the Issuer on December 20, 2012, Amendment No. 1 thereto filed on June 14, 2013, Amendment No. 2 thereto filed on February 24, 2014, Amendment No. 3 thereto filed on July 15, 2014, Amendment No. 4 thereto filed on September 8, 2014 and Amendment No. 5 thereto filed on November 18, 2016 (together, the "Schedule 13D").  All capitalized terms not otherwise defined herein have the meanings ascribed to them in the Schedule 13D.  Only those items amended are reported herein.

ITEM 2. IDENTITY AND BACKGROUND

ITEM 3. SOURCE AND AMOUNT OF FUNDS AND OTHER CONSIDERATION

The aggregate purchase price for the proposed acquisition of the Issuer's river business described in Item 4 below (the "River Business Acquisition") by Sparrow River Investments Ltd. ("Sparrow River") is $73,000,000 and the aggregate purchase price for the proposed acquisition of the Issuer's offshore business described in Item 4 below (the "Offshore Business Acquisition") by Sparrow Offshore Investments Ltd. ("Sparrow Offshore") is $2,500,000.

Sparrow is considering various sources of funds for the River Business Acquisition and the Offshore Business Acquisition reported herein, including funds acquired through capital contributions from its shareholders and/or borrowed funds.  Such funds might be provided from general funds available to the Reporting Persons and the applicable subsidiaries and affiliates thereof, including through capital contributions made by their partners.

ITEM 4. PURPOSE OF TRANSACTION

On November 23, 2016, the Issuer and certain of its subsidiaries entered into an investment agreement (the "Investment Agreement") with Sparrow River, Sparrow Offshore, Fund III and Fund IV, which Investment Agreement is attached hereto as Exhibit J.  Sparrow River and Sparrow Offshore are subsidiaries of Sparrow.  The Investment Agreement sets forth the terms and conditions of the purchase of the Issuer's river business by Sparrow River and, under certain circumstances, the purchase of the Issuer's offshore business by Sparrow Offshore, in connection with the Issuer's previously announced Restructuring.

Under the terms of the Investment Agreement, Sparrow River will purchase the Issuer's river business for $73,000,000, which cash would be used to retire the Issuer's 8.875% First Preferred Ship Mortgage Notes due 2021 and to purchase the outstanding credit facilities with the International Finance Corporation and the OPEC Fund for International Development as set forth in the Restructuring Support Agreement.  In addition, if the Issuer completes its agreement with the lenders to its offshore business to pursue an out-of-court restructuring of the loans to the offshore business, Sparrow Offshore will purchase the equity of UP Offshore (Bahamas) Ltd., which is the direct owner of the Issuer's offshore business subsidiaries, for $2,500,000.

The terms and conditions of the Investment Agreement are described in further detail in Exhibit 99.1 of the Form 6-K of the Issuer filed on November 28, 2016 with the Securities and Exchange Commission and which is hereby incorporated by reference herein.

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO SECURITIES OF THE ISSUER

The information set forth in Item 4 of this Amendment No. 6 is hereby incorporated by reference in this Item 6.