Quoted from djreddog:

The Vacation Bonus base value is 200M. It is increased by 10K at the end of every game played. The only time you can see the Vacation Bonus value is as part of the attract mode on newer machines. On L-3 ROMs, it is not possible to apply the 5X Playfield to the Vacation Bonus - the game merely awards the 200M+change value.
Note: there seems to be some sort of unusual bug which very rarely sets the Vacation Bonus value to exactly 799M. I have actually collected this value (sweet!), and have heard that it's been seen on at least one other machine as well. It seems unlikely that exactly 59,900 consecutive non-Vacation games had been played on two different machines...
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Cows
There are three occurrences of Cows in Whitewater. The first is the fifth item found in Bigfoot's Cave during Bigfoot Hotfoot. Once you have collected that Cow, collecting the Mystery Canyon as a Whirlpool Award the next time during that game will replace the usual Whirlpool animation with a picture of the Spirit pulling a string on the legless Cow, which "MOO"s rather loudly. The picture is labeled "The Secret of the Cow". This picture also appears briefly in the Vacation Bonus award.
The Secret of the Cow is not worth any special points, despite my earlier claim that it was worth 10M.
The third cow in Whitewater is the famous Dueling Cows display, which can be obtained during attract mode. Make sure there are no credits on the machine. It may be necessary to power-cycle first on some machines. Then, press the flipper buttons and start button in the following sequence:
3L 1S 15R 1S 23L 1S
That spells COW. Try it.