Monique Lhuillier Vneck/Vback with a loose trumpet flare dress available at Nordstrom:
(they have added a beading on the waist, my dress does not have any embellishment on the waist)
I fell in love with this dress the moment I put it on - it fits like a glove in the bust, waist, and through the thighs and gradually trumpets out at just the right place (unlike some mermaid dresses that look great when you're standing up straight, but good luck sitting down!)
Our wedding/reception was about 5hrs in total, and I changed right after (total time spent in dress was roughly 8hrs).
***WEARING A BELT ACCESSORY IN PERSONAL PHOTO THAT IS NOT INCLUDED OR ATTACHED TO DRESS***