What are two important factors to consider for estimating departure and arrival times?

Estimating departure and arrival times is crucial for safe and efficient navigation, and tides and currents are significant factors in this process. Tides can affect the water depth in areas such as narrow channels or harbors, potentially determining when a vessel can safely enter or leave a port. High tides may allow for easier access, while low tides can pose navigational challenges.

Currents also play a vital role in travel times. The presence of strong currents can either impede a vessel's progress or aid it, depending on the direction in which they flow relative to the vessel's intended course. Understanding the timing and strength of these natural forces allows mariners to make more accurate predictions regarding how long a journey will take, ultimately improving planning and ensuring safety.

While the other considerations listed, such as weather conditions and crew fatigue, as well as fuel capacity and navigation systems, are indeed important for overall voyage planning, the direct impact of tides and currents on watercraft movement makes them especially critical for estimating departure and arrival times.