Is it a comfort thing? Yes, like everything else in scuba, comfort comes with training and experience.
It is a buoyancy thing? Yes, everything in scuba depends on good buoyancy and trim.
Is it a strong swimming thing? DEFINITELY NOT. If you try swimming hard in scuba, you just burn through your air.
Local ocean currents are often strongest at the surface, and less at the bottom. However in some places, the opposite is true, where some sort of underwater bottle-neck exists, like a dip between two reefs.
The first skill you need to develop for diving in currents is to be able to clear your ears quickly during a fast descent. If the current is strongest near the surface, and less near the bottom, you want to be able to drop down quickly, under the surface current. To do that, you need to be able to clear your ears on descent quickly. Normally you would be descending an anchor line. Even then, descending quickly saves air compared with pulling yourself down hand over hand slowly.
One trick for fast and continuous ear clearing on descent is to press your right hand against the top of your mask, and exhale through your nose on every breath. The slight increased resistance of pressing on your mask with your right hand will act like a mild valsalva procedure, and help your ears to clear more quickly.
The next skill you need to develop is to be able to swim just barely off the bottom, under the current. Since you do not want to scrape against coral, you need good buoyancy skills to do this. The best buoyancy results from proper weighting. Overweighting will make good buoyancy impossible.
Another not so obvious skill you need to develop is the discipline of following your local divemasters. They will be swimming through the crags and crannys where the current is least. You will want to follow them as precisely as possible. If you do not, you will need to kick harder against the current, and your air will then be consumed faster than the others in your group who are following the divemaster better than you are.
There are some swift underwater currents that you can only deal with effectively by holding onto rocky outcroppings. The trick there is to hold on firmly and not let go. You can always pull yourself along with less exertion than it woudl take to kick with your fins against a strong current.
Kicking with your fins always consumes more air than sculling properly with your fins. Your fin movements underwater should always be minimal. On a perfect dive, whether a boat dive or beach dive, you would drop down onto your dive site from directly above with little or no fin action, then hover in the location of your dive with little or no fin action, and then return to the surface after your dive with minimal fin action, all while perfectly neutrally buoyant. That way your air will last twice as long as it otherwise would.
Do not forget your 3 to 5 minute safety stop. In strong currents, the only possible way to accomplish this without being blown downstream away from the boat is to stick to your anchor line. A short jon line for connecting to the anchor line will make it easier to hold onto the anchor line for 3 to 5 minutes in a current.
Be very, very careful in strong underwater currents. Stay with your group. Do not get separated.
Carry an inflatable orange signalling sausage in your B/C pocket or clipped to a D-ring in case you do get washed downstream and the boat has to find you later on the surface.
