"Are you going to swim in the ocean?"
Translation:Unaenda kuogelea baharini?
'are you going to' can imply an action in progress, like someone who is walking towards the ocean, for example. But yes, it can also be interpreted as 'will you'. I'm not sure that it works from Swahili to English, though, because if you mean future interrogative you'd say 'Utaenda' as opposed to 'Unaenda'
I think it would work but it would have a different meaning. "Unaenda kuogelea baharini?" means "are you going to the ocean to swim?" but "utaogelea baharini?" means "will you swim in the ocean?".
The English sentence "Are you going to swim in the ocean?" could mean future or present tense. But given one of the Swahili sentences, only one of the English sentences would work.