This is the time of year lots of anglers along the Texas coast are fishing the jetty systems. The bull redfish run is about to begin and there are still lots of sharks, a few tarpon and some trout to be caught at the rocks from Port Isabel to Sabine Pass. In this photo I took at the Port Mansfield jetties a few years ago I was about 20 yards from the rocks. There were still rocks very close to our boat position that we could not see. At jetties, a good rule of thumb is to recognize that the rocks on the surface only represent about 1/3 of the granite that makes up the structure. If you drew a line down the middle of the rocks going north to south and there was 15 feet on each side that would be there would be 30 more feet out past the visible rocks. If you use electronics, it is easy to see but if not, use the rules of thirds and it will help you to realize there is a lot more to fish than the eye can see. It will also help you from losing weights, anchors, etc.
In addition, if you do not have electronics, pay close attention to areas where the rocks are sunk in a bit. That means there is a deeper hole there washed out by current and that change in depth usually means fish will be nearby.