abstract background corrosion grain grainy grunge metal rough rust texture grungy rock stone armor armored armorment armour armoured armourment backstraps bony ridges crocodile crocodylus-porosus danger dangerous dorsal-surface estuarine-crocodile exotic fauna hide hornback huge Indo-Pacific-crocodile large largest-reptile leather leathery lethargic omnivorous opportunistic opportunistic-predator osteoderms patterns powerful predator reptile reptilian ridges rugged saltwater-crocodile scales scutes skin tail tail-scutes territorial textured textures