dia daoibh,
I was thinking how best to word this. Where I am we would say have a swim. I wasn't sure if it would be the same (to have a swim) in Irish.

De bharr sin, más mian liom snámh a bheith agam/snámh a dhéanamh/a bheith ag snámh ?

(Therefore, if I wish to have a swim...)

GRMA

"Snámh a bheith agam" is like English translated word for word (it sounds like "to own a swim" ).
"Snámh a dhéanamh" sounds weird too.

"Bheith ag snámh" (pronounced "bheith snámh") is the normal way to say it, depending on the sentence ; you can also say "to go swimming" = ghabháil a shnámh (Ulster) or "dul ag snámh" (Munster) or "ghabháil ag snámh" (Connachta)

I'd like to have a swim = Ba mhaith liom ghabháil a shnámh (Ulster)
etc

_________________
Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

Ba mhaith liom dul ag snámh. (goil/gabháil ag snámh, ghabháil a shnámh) = I'd like to go swimming.

"Ba mhaith liom snámh a bheith agam" would mean "I'd like to be able to swim"

go raibh míle maith agaibh aríst