Not being prepared to surf is a common cause of surfing accidents. Surfing requires being fit, being able to swim well and then getting some training. Even the most advanced surfers fall of their boards. 

When that happens you’ll have to locate your board if it isn’t attached to you by a surfboard ankle leash, then paddle back. If you lose your board or it washes ashore, you have to swim back. Either requires a lot of stamina, especially when there are strong currents, which is often the case. Get fit for surfing and ensure that you are a strong swimmer before going out into the water.