To address the high proportion of small target objects in waterborne debris detection, the interference caused by multiple factors such as water surface fluctuations and shoreline reflections, and the high demands on device performance due to the large number of parameters and computational load of detection models, we propose a lightweight, high-precision, real-time detection model, LS-YOLO. First, this algorithm uses the HS-FPN pyramid network design to construct the Neck network structure of YOLOv8. The constructed network structure sacrifices a small part of the accuracy and significantly reduces the number of parameters and computational complexity of the model. Secondly, HS-FPN is improved by introducing the CAA context-anchored attention mechanism to capture remote contextual information to improve detection accuracy. Then, by replacing the loss function with Wise-IoUv3, which features a dynamic focusing mechanism, the detection performance is significantly improved, increasing the robustness of the model. Finally, LAMP pruning technology is used to prune the model to reduce the number of parameters and calculations of the model. The experiment shows that the improved LS-YOLO has a 0.9% increase in mAP50 compared to the baseline model, a 3.2% increase in recall, a reduction in parameters to 19.83% of the baseline model, a reduction in computational cost to 44.44%, and a reduction in model size to 22.22%. The optimized detection algorithm not only significantly improves detection performance and feature extraction accuracy, but also facilitates deployment on resource-constrained hardware platforms.