(Long post alert!) I don't want to blame the mom. But it is an interesting nuance being made in the above posts. Even if mom WAS watching them for all but 10 seconds, but was 50 yards away while watching them, that is not safe when they are 10 feet from the ocean. Another thing that is (IMO) not safe is being outnumbered by children under 5 at the beach. I live near the beach, though not in MA -- and I have two girls, 1 (almost 2) and 3 (almost 4). I've never taken them to the beach by myself before, even though I love the beach... specifically because I couldn't keep tight enough reins on them if they both ran off in different directions, which they do all the time, even with me yelling "stop!" And kids usually run straight to the water, so how can I keep them both safe then? I can't if I'm outnumbered. Since drowning causes the most deaths in their age group, I only go to the beach when my husband or another adult comes along. I may take them by myself when they are 3 and 5...maybe.
That being said... I've lost my 3 year old twice! Once I was in line at a home improvement store, with my youngest daughter in a cart in front of me, and my 3yo standing next to me. While I was setting my items on the register to pay, the 3yo walked away. After loading up my items (10 seconds?) I had looked back to her and saw that she was gone. I immediately panicked and began racing up and down the main aisle, looking down each aisle and calling her name. The store employees started talking on their walkee-talkees, as I was begging them to help me find her. I was horrified, thinking of sex offenders lurking to take little girls by the hand and calmly walk away. I'm sure some of the people who saw me screaming thought I'd been lax watching her. In less than a minute, an employee entered the store with her -- yes, she had walked straight out of the store, where she tried to cross the street by herself! The employee showing up to work had seen her and brought her back in the store, thank goodness. I was mortified, as you can imagine, but so relieved something awful hadn't occurred. I can't imagine never knowing what happened to her after that. I would be a mental case.
The other time, also at a store, my husband and I went in opposite directions to get the shopping done quicker. But he thought dd was staying with me and I thought she was going with him. She walked behind him as he went, but apparently he was unaware of this. So she wandered off. The first I knew about it was when some man walked up and said "Is this your daughter?" in a pleasant voice. I smiled and said yes, thinking he must be someone my husband knew and my husband must be right there too, about to introduce us. But as I realized my husband was nowhere around, and this man was actually handing my daughter over to me, then I was shocked and distraught! He must have thought I was a nut by my initial relaxed reaction. We hadn't even known she was missing for 5 minutes!
So I am not trying to cast aspersions at Caleigh's mom, stuff happens. I have let my 3yo have popcorn and nuts when offered them, even knowing they are choking hazards, because she chews them well and we've never had a problem. I've let my 1yo have a latex balloon when offered, and they are killers of babies too. How this relates is that I have watched closely... but really, what could I do once a popped balloon is blocking an airway? Nothing but panic and watch a terrible situation unfold, just like Caleigh's mom from up on a bridge would been powerless to save her daughter even if she HAD seen her run to the water's edge. I too have taken chances, even though I am well informed of the dangers, and never had a problem. But if we ever DID have a problem, I know I would be subject to the same judgments, especially from myself. :-(
Just because I would never do THIS particular stupid thing, I have done plenty of other stupid things.