Can I dissolve mint in water and drink it?
No, mint won't dissolve in water (leaves are mostly cellulose), but it does make excellent tea.
Boiling water, steep 5-6 minutes.
For best results, I recommending purchasing whole leaf mint intended for use as a tea. That way you can experiment and determine which kind of mint you feel makes the best tea (or make your own blend, I like spearmint tea with a single peppermint leaf thrown in).