Currents describe the movement of water in one direction or another. Be aware that currents can be variable and may change direction as tides or wave actions change. For reasons of safety and comfort, divers need to be aware of the effects of currents and understand the limitations of moving in a current.
Waves generally approach the shore at an angle and rush up the beach at an angle and back following the slope. This action results in water movement along the shoreline. If you did not account for this water movement, you will be pushed away from your intended exit point. So, begin your shore-entry dive upcurrent from your exit point, or dive into the current and drift back to the exit on your return. A dive that carries you along the reef or shore is called a drift dive.
This type of diving can be great fun, but you should log several workup dives in mild current if this type of diving interests you. Also, you should consider taking the drift diving specialty training.
The volume of water carried to the beach by wave actions and tides needs to escape, and it will generally do this along the easiest path. In places with a topography that favors the formation of rip currents, this rush to escape can form narrow streams of fast-running water rushing back out to sea. Many beaches with multiple offshore sand bars or shallow reefs can also produce rip currents.
Rip currents tend to be very strong and can tear you away from the shore quickly. Another factor in the danger of rip currents is that they may form only at certain stages of the tide cycle (for example, just before or just after high tide), and maybe worse during spring tide conditions.
One general guideline, but by no means the only one, is that rip currents are usually formed on beaches with a lot of wave action.
You can usually see a line of turbid, foamy water moving away from shore, and it often will disrupt the waves where it rushes seaward. If you get caught in a rip current, establish neutral buoyancy, and swim across the narrow area of moving water. Never try to swim against a rip current!
When diving in a mild current, always start your dive into the current. Then on your return, the current can assist you back to the shore or dive boat. Avoid surface swims against a current; they will tire you. Rather, swim along the bottom, where the current is usually weaker, if the bottom is in reach of your dive plan. If a current takes you past your exit point, establish positive buoyancy, signal to the dive boat or surface support for help, and wait until you are collected.
You can use currents for drift diving. This type of diving requires more training and practice. You need to follow safety rules and keep a good eye on your buddy or dive professional. It is much easier to get disoriented while drift diving.