Verified answer

While surface ocean currents flow in a regular pattern, they are not all the same. The amount of water flowing and how fast it is flowing differs from current to current. Some currents are deep and narrow, often affected by the shape of the ocean floor, while others are shallow and wide. Some move quickly, up to 3-4 km/hr (1.8-2.5 mph), while others move more slowly. A current can also change somewhat in depth and speed over time.

The water at the ocean surface is moved primarily by winds that blow in certain patterns because of the Earth’s spin and the Coriolis Effect. Winds move the top 400 meters of the ocean creating surface ocean currents. Ocean Currents are of different types. Some currents are deep and narrow. Other currents are shallow and wide. Currents are often affected by the shape of the ocean floor. Some are fast while others are not so fast.

I think the Gulf Stream is fairly predictive..

..from standing on a coastline..I'd guess 20-mph..

I think that it changes all the time..

--fastest a current could travel in a single direction--

I might guess again at 30-mph.

underwater currents have been clocked at up to 25 miles per hour.

yes u cannot say as they change where ever you go

problematic factor. look in google or bing. that will may help!