Fig. 1. The proposed network structure

Fig. 2. The operation process of channel shuffle

Fig. 3. Building blocks of ShuffleNetV2

Fig. 4. Spatial Attention Module

Fig. 5. SAM heatmap

Fig. 6. The structure of SSPP

Fig. 7. Feature map of SSPP

Fig. 8. PANet structure

Fig. 9. Improved PANet structure

Fig. 10. Sample images and labels in SSDD

Fig. 11. Mosaic data enhancement

Fig. 12. Target detection results of the improved algorithm in different scenarios

Fig. 13. P-R curve（the threshold changed from 0.05 to 0.95）

Fig. 14. Comparison of detection algorithms for complex background of near-shore ships

Fig. 15. Comparison of detection algorithms for small target ships in the open sea