Exactly this. If you have events on the beach at night, no swimming signs (even lots of big signs) are not sufficient to warn people that they shouldn't be wading 12 inches from the shore (where, fyi, the water is at most 3 inches deep). People should think about how they see people walking up and down beaches right at the tide line/in the surf; that is much more akin to what this toddler and father were doing than "swimming." During the day, I would say you see 50+ people doing what this family was doing; at night, during an event, I bet there were at least a few others. Whatever warnings they give, this really was not unusual behavior for the area and no one warns you that it might be dangerous.