Wet carpet, won't start?
 

The carpet behind both seats is soaking wet and my '99 Boxster won't turn over - won't crank, although there is battery as the dash lights up.

Thoughts?

Thanks!

Your immobilizer (under the driver's seat) is likely fried. This has been covered ad nauseum in previous posts, just do a search.

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To supplement Ike's post, #1 remove the immobilizer box from under the driver's seat ASAP and attempt to dry it. It may be recoverable. -see searches for immobilizer.
Put this in a search (without quotes): "site:986forum.com immobilizer wet dry"

Find where the water is getting in. 97.465% sure the drains beside the engine compartment are blocked. ...again, a good search will give details.

Open windows and Frunk. Disconnect battery. Leave Frunk open. Get immobilizer out. Clean contacts on cable harness with alcohol or contact cleaner.

Open immobilizer cover and inspect for corrosion. Clean corrosion (wire brush). Spay EVERYTHING with contact cleaner. Place on cookie pan and place in the oven at 150-175 for 20 minutes. Remove from oven and let cool.
No guarantees but doesn’t cost anything to try. Good luck!