"Ann an" = "in a", unless the word starts with B,M,F,P (same rule as the male definite artucle)
When the word starts with B,M,F, or P it changes to "ann am"
Ann an sgoil = in a school Ann am bàta = in a boat Ann am muga = in a mug Ann am preas = in a cupboard
"In the mug" = "anns am muga"
They teach you this in the countries lesson. Dont know which lesson number.
I think all thats right, but to make sure you ought to hop on duolingo on your desk top, and click on the "tips" button instead of the "start lesson button. It explains all of it.
I think it would be 'Tha uisge anns am muga'??? I think adding the s makes the am into the, it's the same with in certain countries if a country has a the infront of it which happens with some countries in gaelic, but I may well be wrong. This is my limited understanding. I'm sure someone can correct me if I'm wrong