An hour from then, he will be swimming.
Student or Learner
What does "I will be swimming in an hour," mean?
Does it mean that the person will be swimming after an hour?
Thank you in advance.
This structure is generally taken as meaning that your swimming will begin sometime within the next 60 minutes and continue beyond that point in time.
It's also possible your swimming began sooner. Perhaps you are swimming already and will continue for another hour at least.
It may be different in BrE.
To me, "I will swimming in an hour" means, as Mike said, that in one hour's time from now, and from that point onwards, I will be swimming.
If someone said, "I will be swimming within the hour", then I would take that to mean, that they will start swimming at any point within the next sixty minutes.
(BrE first language speaker.)
I don't think there is any suggestion of what time the swimming will start. Let's say it is currently 1pm and the following dialogue takes place:
A: I'll call you in an hour.
B: Don't do that. In an hour, I'll be swimming.
All we know is that at 2pm, B will be swimming. B might have started swimming at any time between 1.01pm and 1.59pm.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
And, surprise, surprise, context matters. Say I'm driving to the beach and say "I'll be swimming in an hour" that probably means when I will start swimming.