Deep Currents are slow becuase they are cold and high in salinity. It takes 1 year for a deep water current to travel across the world, while a surface current like the Gulf Stream for example would only take an hour or less.
hey are fastear and this is becasue they have
1. lower nitrogetrn content
2. the salinity is different making for more lubrication
3. the sunlight is less, so ther's less sunburn
4. they're closer to the earth's core
5. radio waves from Mars don't penetrate deeper than 5.88 meters.
6. all the shipwrecks and deep sea rocks slow it down but just a little