While demonstrating the use of an Unmanned Air Vehicle (UAV) to provide a communications relay for surfaced unmanned underwater vehicles (UUVs) at Unmanned Warrior 2016, it became apparent that a closer look was needed to determine the optimal protocol to transfer automatic target recognition image files. Initial efforts with User Datagram Protocol (UDP) were highly unreliable with a very low success rate, despite extensive radio configuration improvements. Afterwards, several protocols were evaluated and UDP-based Data Transfer Protocol (UDT) seemed to provide a good hybrid of the standard transport layer protocols UDP and Transmission Control Protocol (TCP). UDT is an application layer protocol built on UDP with some TCP-like reliability characteristics. This paper documents a careful comparison study of UDP, TCP, and UDT that was performed to determine the optimal protocol for this form of data transfer. Each protocol was used to transfer image files, first in a baseline configuration, then with network emulation packet loss, and finally with real data radios in ideal and then more realistic conditions. Despite that fact that UDT was originally designed to transfer large data sets over high-bandwidth networks, this study demonstrated that it is also ideal for transporting relatively small data sets in high packet loss environments.