Lake is Jheel.

Well, 'lake' is 'jheel'. But 'Irish lake' would not really be 'Irish Jheel', instead it would be 'Ireland ki Jheel'. 'Ireland ki Jheel' would be the equivalent of 'Lake of Ireland'.

But let me give you a complete explanation....

If you wanted to say 'I like Irish Lakes', you would speak 'mujhe Ireland ki jheelein achchhi lagti hain.' [Jheelein is the plural of jheel.]

In Hindi and even in Gujarati, 'Irish lake' would be transformed into the language structure 'lake of Ireland'.

Different languages have a different structure. For instance, 'I like irish lakes' uses the Subject-Verb-Object syntax/sentence structure in English but in Indian languages, the structure followed is Subject-Object-Verb.

Best wishes
Do let me know if there are other doubts
Sincerely
Roomy Naqvy.