bring sand to the beach—come with a girlfriend or boyfriend to a party where there are plenty of single women and men:
- Actually, I don’t suggest bringing any significant other to a club—why bring sand to the beach.
sell snow to the Eskimos—take goods, etc. to a place where they are already plentiful:
- It sounds as sensible as trying to sell snow to the Eskimos, but a Yorkshire company really believes it can persuade us to buy fresh air.