What are the most general fears of people in the world? 

Fear of monsters, animals that we don't really know about or just the fear of unknown, Marine monsters can take many forms, including sea dragons, sea serpents, or multi-armed beasts. In the stories, fairy tales we can find a lot of them. 

A good example of those fears is the Charybdis - a whirlpool, a shipping hazard in the Strait of Messina. The theoretical size of Charybdis remains unknown, yet in order to consume Greek ships the whirlpool can be estimated to about 23 meters (75 ft) across. Charybdis has been associated with the Strait of Messina, off the coast of Sicilyand opposite a rock on the mainland identified with Scylla. Were Charybdis to be located in the Strait of Messina it would in fact have the size to accommodate the whirlpool. A whirlpool does exist there, caused by currents meeting, but it is dangerous only to small craft in extreme conditions.