Template-matching techniques for automatic detection of multiple, extended, and low contrast targets in infrared maritime scenarios are described and analyzed. In particular, we focus our attention on the specific area of the sea around the horizon, where common techniques of clutter removal, based on target contrast only, fail. Targets of interest are ships along the horizon line in adverse atmosphere conditions, with dim contrast with respect to the background. A database of ship images is used for the analysis. We conclude that the normalized cross-correlation (NCC) technique is a reasonable choice for this application due to its capability to provide an estimate of the similarity between images, even if they present different energy levels and are corrupted by noise. It also is more tolerant to the geometric distortions. After a description of the test setup, simulation results are presented to show the performances of the proposed technique; examples using both synthetic and real images are considered.