You planned your dive to avoid swimming into a strong current. The current switched, now what?
Underwater efficiency is essential : Streamline your body, stay horizontal and keep accessories as close as possible. Current is rarely uniform, so you may be able to escape a strong current by swimming across it until you reach an area of weaker current.
Kick mostly from the hips, not the knees.
Keep your strokes as small as reasonably possible so fins stay within the slipstream of your body. Wider kicks create more drag and are less efficient.
Keep your fins completely under water; kicking the air is wasted energy. On the surface, roll onto your back. Or submerge about 15 feet.
Pace yourself. This is an endurance event, not a sprint, so back off from top speed. Monitor your breathing rate and slow down before you run out of gas.
Streamline Your Body
Be horizontal. You want to bore the smallest possible hole through the water. Adjust your buoyancy carefully so you are not finning upward as well as ahead. If you're finning on the surface on your back, don't let your butt sink.
Trail your hands and arms. Keep them still at your sides. Stroking with your arms adds little propulsion and costs dearly in energy.
Keep accessories close to your body. Consoles and accessories should be held as close as possible so they hide a little in your body's slipstream. A camera, for example, should be held close to you with its broadest surface turned parallel to your direction of movement.
Dump extra weight. If this is going to be a difficult swim, better drop that game bag. If it's really hard, dump your weights. If it's life-threatening, say goodbye to the Nikonos. Bulk and weight both mean drag.
Still Not Making Headway?
Dodge the current. Current is rarely uniform everywhere. It is usually stronger at the surface, around points of land and through narrow passes. Swim cross-current out of the high-current area or go to the bottom.
Hand-to-hand. If the current is too strong, you can pull yourself along the bottom by grabbing rocks, dead coral, etc., or stick your knife into the sand and pull on that.
Get ashore. If all attempts fail, swim across the current toward the nearest shore and get out of the water, taking care not to be injured by surf or rocks. Your risk of injury will be lower and your chance of being found will be higher on land than in the water.