There's a very big difference between pool swimming and open water swimming, not least making sure that the waves are not too strong for you. In a pool, there are no waves, you are in total control, provided you can swim. In open water, the waves are unpredictable, no matter how strong a swimmer you are. You also have to be sure there are no rip tides. When swimming in open water, make sure you do not go alone. Take an experienced companion with you, at least your first few times and check up on any new sites you are gong to, to ensure there are no special conditions you need to be aware of.