This crocodile is showing off a common pose, basking in the sun with mouth agape. Do they do this to look intimidating? Are they hoping some animal will wander close enough for it to snap down and have a snack? The reason is actually a lot more practical than all this.
Crocs and gators hang around with their mouths open as a way to avoid overheating. Keeping cool may be the primary purpose but for some species there's a secondary gain from the behavior. For crocodiles living in the range of the Egyptian plover, or "crocodile bird," sitting around with your mouth open means you might get a teeth cleaning from one of these small birds. The plover acts as both a dental hygienist and a warning system for danger.
PawNation writes, "The plover comes along and, using his sharp little beak like a toothpick, removes the bits of meat from between the crocodile's teeth. This feeds the plover and removes parasites from the croc's mouth. The plover serves as a security alarm system for the crocodile. If, while in the croc's mouth, the plover senses danger from an oncoming animal, she screams and flies away. This behavior alerts the crocodile to the imminent danger, so he can slide into the water and out of harm's way as well. In this way, the plover keeps her source of free food safe for future use -- a service the croc, no doubt, appreciates regardless of the motive."