Periophthalmus barbarus, the Atlantic mudskipper. Mudskippers spend much of their life out of water, resting on rocks, roots or anything else they can find to perch on. They walk by using their highly modified pectoral (swimming) fins much like legs.
Mudskipper are able to burrow into sediment because they are cutaneous breathers. They can - through their skin & mouth/throat lining - breathe in the small bubble of air around them as long as they stay moist.