What signals is required of a powerboat that has the run aground during periods of restricted visibility?

A powerboat that has run aground during periods of restricted visibility is required to sound a signal of one long blast followed by two short blasts at intervals of not more than two minutes. This signal alerts other vessels to its situation and indicates that it is not making way. Additionally, the vessel should display appropriate day shapes, such as a ball shape, to indicate that it is aground.