There is a chance that the liquid damaged it, in which case the cheapest solution would probably be to pick up a used/refurbished Nexus 7.
However, there is a solution to the Nexus 7 getting stuck on the splash screen while booting that I've seen on IDG Answers before. It sounds weird, but it has worked for a lot of people - tap firmly on the back of the tablet while it boots. Not too hard, don't go overboard, just repeatedly tap on the back while it boots up.
Here is a step-by-step from the previous post:
"1. Switch off nexus device.
2. Press power and lower volume button together to enter in to service mode.
3. Press the volume up button to select START appears in the display.
4. Now press power button to start your device.
5. Google logo will appear and stuck, now just tap at back side from top to bottom as gently.
6. After few tappings,if still stuck then connect the charger and tap again for few times gently.
7. I am sure your device will start."