What were some of the dangers and consequences that portuguese sailors might have worried about when setting off on a journey along the west coast of africa in the early 1400s?

1.huge monsters capable of swallowing whole ships existed in this one great sea
2. the sea began to boil the farther south you travelled
3. the world was flat and the ship could fall off the edge of the world.4. shipwreck due to storms
5. getting washed overboard during bad weather
6. suffering from diseases such as typhoid (from bad water) and scurvy (from lack of vitamin C)