Audio unit mountable in personal watercraft

An audio unit mountable in a personal watercraft, comprising:

• a speaker;
• an automated adjustment device connected to the speaker for automatically adjusting a volume of a sound emitted from the speaker such that the volume of the sound becomes an automated sound volume value corresponding to an engine speed or a watercraft speed;
• and
• a sound volume manipulation member configured to be manipulated by a rider to change the volume of the sound emitted from the speaker with respect to the automated sound volume value,
• wherein when the engine speed or the watercraft speed satisfies a predetermined deceleration condition, the automated adjustment device cancels a sound volume increase amount with respect to the automated sound volume value which was caused by the rider's manipulation of the sound volume manipulation member before the predetermined deceleration condition is satisfied and adjusts the volume of the sound emitted from the speaker such that the volume of the sound becomes the automated sound volume value.