Water resistance is not the same as waterproof
Many recent iPhone models have laboratory-rated splash and water resistance, but Apple states that resistance can decrease with normal wear. A wet speaker may sound muffled until water evaporates. The presence of a rating does not mean the phone should be intentionally submerged or charged while a connector is wet.
After freshwater exposure, wipe the iPhone, hold the connector downward and leave it in a dry place with airflow. Apple advises against heat and compressed air. A guided browser sound may help droplets near the loudspeaker opening move outward, but it does not confirm that the inside is dry.
Bottom speaker or top receiver?
Music, videos and speakerphone usually use the loudspeaker system near the bottom edge. Normal calls use the receiver above the display. If calls are quiet while media sounds normal, inspect the receiver slot and make sure a screen protector or case is not covering it. If all audio is muffled, focus on water, settings, routing and the loudspeaker opening.
Use the Call Speaker Cleaner routing test because web audio may still play through the bottom speaker rather than the receiver. Do not assume a tone has reached the earpiece without listening at both locations.
Safe cleaning for an iPhone speaker opening
Power the iPhone off and unplug it. Use a clean, dry, soft-bristled brush over a blocked speaker or receiver opening. Keep the opening downward and use light strokes. Do not insert a sharp object, apply liquid into the mesh or use canned air.
If the iPhone has severe crackling, no sound, a liquid-detection warning that does not clear, or other functions changed after a splash, stop repeating tones and contact Apple or an authorised service provider.
A useful before-and-after test
Play the same voice memo, ringtone or spoken video at a fixed moderate volume. Check for clarity, balance and buzzing. Then make a normal call and compare the receiver separately. This avoids judging success only from the unusual low-frequency cleaning sound.