Except that the pool area appears to be intact. While the pool deck may be the proximate cause, it's premature to focus on that to the exclusion of a real investigation.
I take the pool deck as being the whole area up to the doors, since there were patio tables and lounge chairs almost all the way to the entrance. Also, some planters.
But reading Petitfore’s link certainly has me thinking the building was undermined. The leaking from above the garage didn’t help. but a frequent foot or more of seawater in the garage definitely sound like a big deal.
“ “ Mike, a political strategist, was on a business trip to Washington when Cassie called him at 1:30 in the morning, frantic that the building had shook. She was on the phone with him when she looked out the window and saw a sinkhole where the swimming pool had been. Then the line went dead.””