UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 1, 2015

ODYSSEY MARINE EXPLORATION, INC.

(Exact name of registrant as specified in its charter)

5215 West Laurel Street

Tampa, Florida 33607

(Address of Principal Executive Offices and Zip Code)

Registrant’s telephone number, including area code: (813) 876-1776

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

On October 1, 2015, Odyssey Marine Exploration, Inc. (“Odyssey”) and Odyssey Marine Enterprises, Ltd., an indirect, wholly owned subsidiary of Odyssey (“Enterprises”), entered into an Amendment No. 2 to Promissory Note (the “Amendment”) with Minera del Norte S.A. de C.V. (“MINOSA”). The Amendment further amends Section 2(a) of the Promissory Note, dated as of March 11, 2015 (as amended by Amendment No. 1 thereto dated as of April 10, 2015, the “Promissory Note”), among Odyssey, Enterprises, and MINOSA to provide that, unless otherwise converted as provided in the Note, the adjusted principal balance shall be due and payable in full upon written demand by MINOSA; provided that MINOSA agrees that it shall not demand payment of the adjusted principal balance earlier than the first to occur of: (i) 30 days after the date on which (x) SEMARNAT makes a determination with respect to the current application for the Manifestacion de Impacto Ambiental relating to the Don Diego Project, which determination is other than an approval or (y) Enterprises or any of its affiliates withdraws such application without MINOSA’s prior written consent; (ii) termination by Odyssey of the Stock Purchase Agreement, dated March 11, 2015 (the “Purchase Agreement”), among Odyssey, MINOSA, and Penelope Mining, LLC (the “Investor”); (iii) the occurrence of an event of default under the Promissory Note; (iv) December 31, 2015; or (v) if and only if the Investor shall have terminated the Purchase Agreement pursuant to Section 8.1(d)(iii) thereof, March 30, 2016.

The Amendment also prohibits Enterprises, Odyssey, and the respective subsidiaries from (a) prepaying any indebtedness so long as any adjusted principal balance of the Promissory Note is outstanding or (b) granting any encumbrance on any of their property or assets, and provides that any breach of these covenants constitutes an event of default under the Promissory Note.

The foregoing description of the Amendment does not purport to be complete and is qualified in its entirety by reference to the full text of the Amendment, which is attached hereto as Exhibit 10.1.

Not applicable.

Not applicable.

Not applicable.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.