Normal earplugs are usually ineffective. In fact, they may do more harm than good. When plunging, they produce airspace that cannot be equalized. The surface tension of water prevents sudden pressure fluctuations from reaching the eardrum and producing discomfort. However, if the pressure changes are large enough to burst blood vessels in your ears, then you should seek medical attention immediately. It is important to understand that earplugs are only effective when worn properly. If you leave them in all day every day, they will lose their protection. Also, make sure that you aren't blocking your own exits when diving. For example, if you are a no-fins diver and wear earplugs, you should not go straight back into the pool after swimming because you will need to clear out your ears before entering another body of water. Earplugs are available in many different shapes and sizes. It's up to you how much protection you want from underwater noise, but too few plugs will not provide enough relief for your ears. Too many plugs will cause problems of their own such as hearing loss and damage to the inner ear. Try some out before going under the water to find what size fits best without causing other issues.