Waves wash onto beaches anything floating on or under the water. Long lines of seaweed drying out in the sun are left on the beach. The lines of seaweed marks where the previous high tides reached. In this photo the second last tide was much higher than the last tide leaving two lines of seaweed.
Most of the drying seaweeds were fixed to rocks or the sand and have broken away. Among the seaweed there can be shark eggs, dead fish and crabs, shells, sea stars, sea jellies and many other remains of animals.
There can be some living animals such as crabs and sand hoppers. Many sea birds visit the beach to find food that has washed up with the waves and tide.
After storms there will be a lot more material washed onto the beach. Many beaches also have litter. Nearly all this litter has been washed from the land through stormwater drains. Whenever there is a lot of stormwater litter on the beach, the sea will also be polluted.