Mary,

If you can't sail faster then the current, drop the anchor.

That's all.
The rest is just a description of how I won a race doing that...

I was 17 and it was the second race in the family's new monohull (29 ft). Just after the start there was almost no wind in the Guanabara Bay, Rio. Then I noticed that all boats were moving backwards very slowly due to the tide and sent a crew member to drop the anchor in great secrecy.

It was magic: for the others it seemed that we had a private puff or something. When they found what we did, it was too late - we were leading the race. When the expected thermal headwind arrived, it helped us increase the lead to win the race with a certain ease.

But your nightmare reminded me of another race. We anchored due to the tide 100 ft from the finish line - for one hour. Not a pleasant experience.