Lane

[Jellybaby]

¿Cómo se dice..?

"She was swimming in the middle of the lane."
"Estaba nadano en el medio del carril."

"Now you've got the whole lane to youself." (to swim in)
"Ahora tienes todo el carril para tu misma."

[asensiofj]

In that case, in Spain and in a swimming pool, a "LANE" is "UNA CALLE".

So...."Estaba nadando en el medio de la calle" (de la piscina)
"Ahora tienes toda la calle para TI misma" (nadando en una piscina)
If you are in the sea, it doesn't make sense.