Indonesia's marine ecosystems, part of the globally recognized Coral Triangle, are among the richest in biodiversity, requiring efficient monitoring tools to support conservation. Traditional fish detection methods are time-consuming and demand expert knowledge, prompting the need for automated solutions. This study explores the implementation of YOLOv10-nano, a state-of-the-art deep learning model, for real-time marine fish detection in Indonesian waters, using test data from Bunaken National Marine Park. YOLOv10's architecture, featuring improvements like the CSPNet backbone, PAN for feature fusion, and Pyramid Spatial Attention Block, enables efficient and accurate object detection even in complex environments. The model was evaluated on the DeepFish and OpenImages V7-Fish datasets. Results show that YOLOv10-nano achieves a high detection accuracy with mAP50 of 0.966 and mAP50:95 of 0.606 while maintaining low computational demand (2.7M parameters, 8.4 GFLOPs). It also delivered an average inference speed of 29.29 FPS on the CPU, making it suitable for real-time deployment. Although OpenImages V7-Fish alone provided lower accuracy, it complemented DeepFish in enhancing model robustness. Overall, this study demonstrates YOLOv10-nano's potential for efficient, scalable marine fish monitoring and conservation applications in data-limited environments.