SWAGSplatting: Semantic-guided Water-scene Augmented Gaussian Splatting

Abstract

Accurate 3D reconstruction in underwater environments remains a challenging task due to light attenuation, scattering, and limited visibility. While recent AI-based approaches have advanced underwater imaging, they often overlook high-level semantic understanding, which is crucial for reconstructing complex scenes. In this paper, we propose SWAGSplatting, \textit{Semantic-guided Water-scene Augmented Gaussian Splatting}, a novel multimodal framework that integrates language and vision knowledge into 3D Gaussian Splatting for robust and high-fidelity underwater reconstruction. Each Gaussian primitive is augmented with a learnable semantic feature, supervised using CLIP-based embeddings extracted from region-level semantic cues. A dedicated semantic consistency loss enforces alignment between geometric reconstruction and scene semantics. In addition, a stage-wise optimisation strategy combining coarse-to-fine learning with late-stage parameter refinement improves training stability and visual quality. Furthermore, we propose a 3D Gaussian Primitives Reallocation strategy to address the imbalanced distribution of primitives introduced by naive point cloud densification. Extensive experiments on the SeaThru-NeRF and Submerged3D datasets demonstrate that SWAGSplatting consistently outperforms state-of-the-art methods across PSNR, SSIM, and LPIPS metrics, achieving up to a 3.48 dB improvement in PSNR, enabling more accurate and semantically coherent underwater scene reconstruction for applications in marine perception and exploration.