1997 Porsche Boxster Water damage

White smoke from the exhaust is normally a sign of burning engine coolant from a leaking cylinder head gasket, but in this case, water could have gotten into the exhaust system and is boiling off. You didn't say if this was a hard rain storm or the car was submerged for hours. Was the engine running at the time or just sitting outside? If engine performance is normal, and the coolant level is not dropping, the problem should clear up on its own. If the coolant level IS dropping, you can verify a leaking head gasket by adding a small bottle of dark purple dye to the coolant, then check later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. If the head gasket is leaking, you'll see the dye inside the tail pipe.

Having a hard time understanding that description. Based on the smoke, I'd have your mechanic do a chemical test at the radiator for a leaking head gasket. If that is negative, use the dye in the coolant, then check inside the tail pipe.

Nothing you've said so far really suggests water damage. Typically the car needs to be submerged above the bottoms of the doors before there's cause for concern. Brakes can get wet from driving through deep water, but those will dry off very quickly.