No. This law, effective 9/1/2001, prohibits the possession of an open container of an alcoholic beverage in the passenger area of a motor vehicle. It does not apply to watercraft. http://www.tpwd.state.tx.us/faq/warden/boatinglawfaq.phtml
An "open container" is as the name implies. The seal, or bottle top, or pop-top, or whatever, was opened (i.e. - not as sealed from the factory). "Possession" is simply "having" the contraband in your possession whether or not it was opened.
Zero Tolerance as far as I know. Lets get some some more questions answered though: How old is the person in question? Was the alcohol in an open container? Was the said person driving? (With or without the alcohol being opened) If they were under the influence, how much did blow? Let me know...
If left open, yes. It's because alcohol is highly volatile. However, if kept in a closed container, it will not evaporate. Instead, it will be oxidized by the oxygen gas in the container to form the corresponding acid of the alcohol.