Tina Knowles -- Wedding Day #2!

Tina Knowles is getting hitched for the second time, this time on a fancy yacht ... with Beyonce and Jay Z on board!

Beyonce's 61-year-old mom is marrying 67-year-old actor Richard Lawson on Sunday evening -- and the yacht is cruising around the harbor in Newport Beach, CA.

Everyone is dressed in white, including Blue Ivy. Solange was also there along with other relatives. The boat holds 300, and we're guessing they could fill it to capacity if they want.

Tina and Beyonce showed up around noon to check out the boat. They left together in an SUV before returning for the ceremony.