In the maritime environment, Situational Awareness (SA) is a crucial task for many applications, including the defense of the naval tactical space. In this context, Electro-Optical (EO) sensors and, particularly InfraRed (IR) sensors, contribute to building the Local Area Picture (LAP). The purpose of this study is to face the challenging task of highlighting extended targets with respect to the open sea background without any prior knowledge about the size and position within the images. In this work, only single-frame object detection algorithms have been considered. As this task has been extensively explored in the three-channel color image domain, we adapted some color native state-of-the-art strategies on the IR monochromatic dimension. The algorithms have been tested on a dataset collected through a cooled Medium Wavelength (MW) sensor and an uncooled Long Wavelength (LW) sensor. The ground truth (GT) has been built through direct observation. Each technique has been then evaluated on the two sub-bands images according to broadly used performance indices.