The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
You did not mention any specific time in history, so we are going to assume that you are referring to the present moment.
The possible environmental hazards that were involved in crossing the ocean are the following. First, the oceanic currents, then the heavy storms and the huge weaves formed during storms in the sea. Bad weather is one of the most complicated things when sailing a ship in the ocean. Then, another hazard is thunder and lighting.
All of these hazards and environmental issues can affect the technology of the ship in the middle of the ocean. Navigation systems can be affected and communication systems can malfunction.
