Hi Ellie and welcome to the forum:
The bad news is that you can't fix it or get it fixed. Once a camera is compromised by water it is a write-off. No Canon service centre would touch it. The reason is that water, even rain water or drinking water, has pollutants in it and various chemicals that will attack the circuitry and oxidize it. Also, once water gets into the lens it will inevitably encourage the growth of fungus.
So, the best bet is make an insurance claim if you can and get a new camera. Check out the point and shoot cameras available from the Canon Refub site - these are 'good as new' and come with a Canon warranty.
The PowerShot 810 may not be available now but there are some really excellent cameras of the same point and shoot style. Just keep scrolling down the list of gear!
Canon Refurbished & Used Cameras & Accessories | Canon U.S.A, Inc.
cheers, TREVOR
The mark of good photographer is less what they hold in their hand, it's more what they hold in their head;
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
