Dead low waters refer to the lowest tide levels in the ocean. There are several synonyms for this term, including low tide, neap tide, ebb tide, and slack tide. Each of these terms describes different aspects of the ocean's tides. Low tide refers to the ocean's tide at its lowest point, while neap tide describes a tide that occurs at the halfway point between low and high tide. Ebb tide refers to the outgoing tide, which causes the water level to decrease, while slack tide describes a period of no tide movement. Each of these terms can be used interchangeably with dead low waters, depending on the context in which they are used.