UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)*

ULTRAPETROL (BAHAMAS) LIMITED

(Name of Issuer)

Common Stock, Par Value $0.01 Per Share

(Title of Class of Securities)

P94398107

(CUSIP Number)

José Antonio Sastre G.

c/o SIPSA S.A.

Av. El Bosque Norte 0440 of. 1101

Las Condes

Santiago, Chile

Tel: (011) (56) (2) 362-3333

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

February 18, 2014

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  x

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

This Amendment No. 4 to Schedule 13D relates to shares of the Common Stock, par value $0.01 per share (“Common Stock”), of Ultrapetrol (Bahamas) Limited., a Bahamas corporation, and amends the initial statement on Schedule 13D filed on July 22, 2010, Amendment No. 1 thereto filed on November 19, 2012, Amendment No. 2 thereto filed on December 12, 2012, and Amendment No. 3 thereto filed on June 17, 2013 (together, the “Original 13D” and, together with this Amendment No. 4, the “Schedule 13D”). Capitalized terms used but not defined in this Amendment No. 4 shall have the same meanings ascribed to them in the Original 13D.

ITEM 4. PURPOSE OF TRANSACTION

The disclosure in Item 4 of the Original 13D is hereby amended by adding the following.

On February 18, 2014, Hazels exercised the Warrant, and thereby obtained Class B shares representing all the economic interests in Sparrow 2, which holds 16,060,000 shares of Common Stock. Under certain circumstances, including the sale by Sparrow of all of its Common Stock, the Class A common stock of Sparrow 2 will be canceled, and the Class B common stock will come to represent all of the voting interests in Sparrow 2. Each of the Reporting Persons has already reported beneficial ownership of these shares of Common Stock because they are covered by the terms of the Shareholders’ Agreement, and accordingly, the Warrant exercise does not change the share ownership amounts reported by these persons.

ITEM 5. INTERESTS IN SECURITIES OF THE ISSUER

The disclosure in Item 5 of the Original 13D is hereby amended by deleting paragraph (c) therein and replacing it with the following.

(c) On February 18, 2014, Hazels exercised the Warrant and thereby obtained Class B shares representing all the economic interests (but none of the voting interests) in Sparrow 2, which holds 16,060,000 shares of Common Stock. These shares of Common Stock remain subject to the terms of the Shareholders’ Agreement.

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

Item 6 of the Original 13D is hereby amended by deleting in its entirety the subsection entitled “Warrant” and by amending and restating the subsection entitled “Sparrow Shareholders’ Agreement”) to read as follows.

Sparrow Shareholders’ Agreement

The Sparrow Shareholders’ Agreement sets forth the agreements of the parties thereto regarding, among other things, the governance of Sparrow 2, the transfer of their shares of Sparrow 2, and the potential “earn out” payment to Hazels. Sparrow 2 is a company that will, after the Closing, hold 16,060,000 shares of Common Stock. Sparrow owns all of Sparrow 2’s Class A common stock and therefore all of its voting power. Upon its exercise of the Warrant, Hazels obtained all of the shares of Sparrow 2’s Class B common stock, which represent all of the economic interests (but none of the voting interests) in Sparrow 2. The provisions of the Sparrow Shareholders Agreement include the following.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, the undersigned certify that the information set forth in this statement is true, complete and correct.

Dated: February 25, 2014