Currents and Waves

• Changes in the ocean water near the shoreline can have life-threatening results for individuals swimming or surfing in these areas. Riptides, caused by powerful currents within confined areas, can present a danger to people, especially surfers, as they are difficult to fight against and can push individuals further out into the ocean than is safe. Especially strong currents can also arise anywhere in the ocean, and may have the same effect if they push an individual away from the shoreline and the person isn't a strong enough swimmer to paddle back to safe waters. Huge waves may also be a threat, as these can push swimmers down and could lead to drowning in some extreme cases.
  
  

Ocean Creatures and Swimmers

• The ocean is full of creatures that can attack nearby humans. Typically, marine animals strike because they're provoked or because they mistake a human for their usual prey. Some coastal areas often see shark attacks, which can result in nasty wounds or worse, as the shark bites a human after mistaking it for a fish. Crabs can pinch the feet of people walking on the ocean floor, while jellyfish might sting those swimming in the ocean.
  
  

Storms

• Boats on the ocean can be vulnerable to storms, often with especially strong winds, which can cause damage. Storms can also lead to visibility problems for those trying to navigate on the ocean, and result in vessels heading off-course. In extreme situations, boats can be sunk by the conditions generated by storms.
  
  

Tsunamis

• Ships on the ocean are also vulnerable to the effects of tsunamis, huge waves that typically result from the eruption of volcanoes underwater. In extreme circumstances, such waves can entirely cover boats and cause significant damage. Boats are more vulnerable when they're close to shore, with vessels further out into the ocean having less chance of being threatened by a tsunami wave.
  
  

Animals Ramming Boats

• Another danger to ships on the ocean comes in the form of large animals that can ram boats and even overturn smaller vessels. The chief culprits are marine animals such as sharks and whales, which can attack if irritated. According to the website The Oceans, these attacks are quite rare. Even so, ship crews can do little to deter such animals, if they do appear.