Open water swimming GPS not always available?

[Yves_]

The Suunto Run probably won’t be the optimal watch for this, but swimming is also available there. I tried it today and was surprised that it tried to record a route once and not the second time. Although in this case, it was pointless; I was just swimming against the river current

Is there any way to influence this, or is it simply because the watch hasn’t been out of the water enough?