At the secret beach, go all the way up (by pressing UP on the D-pad), then go all the way left. There'll be a small series of ledges to climb.

When you get to the top, there'll be bamboo sticks, which you can use to make a fishing rod out of (if you have a vine as well), or make a spear (if you have a vine and a sharpened rock) to fish with to pass the time if the tide goes up.

You can also shake the bamboo trees for some sticks. Take some to Skye so she can make some stuff for you. Also on the ledge, there are bamboo shoots that you can eat if the tide gets high, or take them to Skye to cook.