## 1 Introduction  
Approximately 71% of the Earth's surface is water-covered; this water is usually split between the oceans and small-scale seas, but the oceans have \(\sim\)96.5% of Earth's water. Ocean warmth command environment and wind originals that change life on earth. Freshwater in lakes and rivers comprises less than one percent of the Earth's surface water. Countless efforts have been made by the researchers and scientists to discover this undiscovered massive amount of oceans water, but unfortunately the much of the ocean remains undiscovered. The developments in the last several decades in hardware and communication techniques have guided current advances in underwater activities, such as environmental monitoring, moneymaking or research exploration, and harbor protection. The employment of the Internet of Underwater Things (IoUTs) is an optimal system for these tasks. The IoUTs are described as a global network of intelligent, interconnected underwater things that allow controlling of large unexplored water areas [1]. The edge devices collected information is transferred to the sink node, this gathered information can be analyzed and serviced by using ground support units. Generally, underwater communication is still a big challenge due to the oceanic environment physical characteristics. There are four communication technologies used as a physical layer for underwater communication: optical, electromagnetic, magnetic induction, and acoustic waves. Until now, the acoustic waves is the most used one in long distance underwater communication [2; 3]. However, the acoustic bandwidth is limited, and it consumes high power transmission and IoUTs nodes are battery-based with no capability for recharging. Therefore, multimedia data transmitting, such as image and video, is a big challenge especially for real-time IoUTs applications. The next generation of the underwater acoustic communication techniques should be focused on improving transmission data rate to support real-time underwater multimedia applications. However, a high-speed wireless transmission over underwater channel is more complicated compared to the radio links [4]. Underwater multimedia applications can be improved via two research directions: First, by using high-compression encoder techniques, and the second direction is by using effective communication schemes that deal with underwater acoustic channel bandwidth limitations. In line with the first research direction, set partitioning in hierarchical trees (SPIHT) image coding has been proposed and introduced in [4]. The SPIHT algorithm is providing the best peak signal-to-noise ratio (PSNR) condition of the obtained decoded image for addressing compression ratio. The SPIHT coder based on wavelet algorithm is the most employed algorithm in image compression as well as being an essential type of compression for all subsequent algorithms. Spatial modulation technologies have been proposed to deal with the second research direction [3; 5]. There are some other research articles, where researchers tried to tackle with improving the underwater multimedia application using combined ideas of two research directions: unequal error protection (UEP) techniques via hierarchical quadrature amplitude modulation (HQAM) [4; 6]. In the UEP, the robustness of the transmitted image quality can be significantly increased. The key of UEP approaches can be classified into three main types: (1) joint source-channel coding, by providing the optimal source/channel coding rate; (2) rate allocation, by supplying and optimizing fixed channel rate over source packets; and (3) utilizing modulation systems given different protection levels to different conveyed bits. In line with UEP utilizing modulation systems, this paper proposes a new UEP scheme based on spatial modulation for image transmission over IoUTs to combine high compression SPIHT encoder technique with highly efficient transmission spatial modulation (SM) scheme.