To increase your chances of catching from the sea you need to be there when the fish are hunting on that mark. Tide is a huge factor in this.
Generally larger tides induce more fish in to feeding, because stronger currents scourer food from the sea bed and higher tides flood beaches and rock dragging food sources into the sea. Also higher tides are often when other sea creatures mate and give birth hence a lot of planktonic food stuffs in the water column. For example mysis shrimp are found in my experience in greater numbers when there is a full moon, hence spring tide.
I would suggest as a rule of thumb the last hour of a rising tide and the first two hours down are the prime times, this said some marks fish best at low water, or just on the flood so you will need to try and see what fishes best.
Another factor is daylight. The bigger predators generally hunt closer to the shore as it gets dark, so a spring tide in the evening or early morning would be you best option for a first attempt at a new mark.
For more information have a look here – Tide and how it effects sea fishing