Typically, these people send their young ones down between 7 & 8 am to make reservations then they don't arrive until 10 am when the life guards go on duty. I've seen people block (I like that word) a table and not show up until after noon.
According to DH, it's usually the dad who has that duty or grandpa who's up getting his mug of coffee.
They went from that front row all the way back to the community center.
If the owners weren't there, the stuff was gone! I often heard grumbling about the person who moved the stuff at the pool; it made me feel like James Bond
I'm not as agile on the sand in the day, it wouldn't work for me at night.