Going from swimming in a pool to swimming in open water is not easy. You might need to adapt to a few factors before you feel comfortable: the water temperature, finding your way in the water, the outdoor weather, etc.
In the swimming pool, corridors can help us find our way. In open water, if we do not look towards where we are going, we can easily deviate from our trajectory. It is therefore necessary to develop appropriate swimming techniques. To do this, it is recommended that you consult a trainer who can provide you with sound technical advice.
We must also keep in mind that this type of swimming can be more physically demanding depending on the strength of the current or the presence of waves. The idea is therefore to set goals adapted to your level. If you want to train for an event like a triathlon, it may be useful to start by working on your endurance in the pool before starting to train in open water.