1.20 Ability

	General ability	Ability on a specific occasion	No ability
Past time	I could swim ¹	I was able to swim ¹ I managed to swim ¹ I succeeded in swimming¹ I could have swum ¹	I couldn't swim I wasn't able to go
Present time	I can swim		I can't swim
Future time	I will be able to swim ²	I will be able to swim I will manage to swim	I won't be able to swim

¹ Compare:

I could swim when I was six.
(Sabía nadar cuando tenía 6 años.)

The ship sank, but I managed to swim/was able to swim/ succeeded in swimming to the island.
(El barco se hundió, pero pude nadar hasta la isla.)

I could have swum to the island.
(Podría haber nadado hasta la isla.)

We cannot say:

The ship sank, but I ~~could~~ swim to the island.

² We cannot say:

I ~~will can~~ swim