Act quickly
Time is the critical factor with water damage. The moment current passes through wet electronics, corrosion begins at every exposed metal contact. If your camera gets wet, remove the battery immediately to stop current flowing, take out the memory card, and do not attempt to power it on. Leaving it overnight in a bag of rice is a popular home remedy but it is rarely effective for anything beyond surface moisture. Bring it to Tim as soon as possible.
What the assessment involves
Tim opens the body and inspects the internals for corrosion, short-circuit damage, and the presence of mineral deposits that indicate the water penetrated beyond the outer shell. Fresh water with low mineral content causes less damage than sea water (salt accelerates corrosion dramatically) or chlorinated pool water. A board that has only been briefly wet can often be cleaned with appropriate solvents and contact restorer. Heavy corrosion on the main PCB or sensor flex is harder to address and Tim will tell you clearly if a board-level fault is beyond practical recovery.
Weather-sealed bodies
Weather-sealed DSLRs and mirrorless cameras (rated IPX4 or equivalent) are resistant to rain and splash but not submersion. The seals around buttons, dials, and the card slot can degrade over time. A body with aged seals offers less protection than its original rating suggests. If a sealed body has been submerged or exposed to sustained heavy rain, it should still be assessed, as the ingress routes for water differ from an unsealed body and the recovery process varies accordingly.