Formal:

* Ebb tide: This is the most common alternative to "low tide," referring to the period when the tide is going out.

* Neap tide: This refers to a particularly low tide that occurs during a phase of the moon when the gravitational pull of the sun and moon are opposing each other.

Informal:

* Slack water: This refers to the brief period of time when the tide has stopped flowing and is about to change direction.

* Dead low: This is a very low tide, often used by fishermen and boaters to navigate shallow waters.

* Low water: This is a general term for the time when the tide is at its lowest point.

The best term to use will depend on the context. If you're talking about a specific type of low tide, you might use "ebb tide" or "neap tide." If you're just talking about the general phenomenon of the tide going out, "low water" or "low tide" will suffice.