This is a Sea Turtle Nest. It is nesting season so there are a ton of them all over the beach right now. They are clearly marked with cones with cute little turtles on them. They also have signs explaining what they are and not to disturb them. Sea Turtles are protected and the local wildlife, turtle tracker people make great efforts in keeping track of and keeping these babies safe.
The nests are labeled with numbers. If you look closely this one is B23 and the dates for laying and expected hatching are on the post. If you have never seen a hatching it is up on the list of very coolest things ever!
This is what it looks like when the Turtles come in and go back to the water when they lay their eggs. Turtle Tracks!
Have an excellent day!