Quoted from John_I:

The home ROM, Version LH-6 is the bomb for WH2O. It fixes a lot of bugs and completes the software nicely. A lot of game were never updated to this. They all should be. Even if you turn off the ball saver.
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Home Version LH-6:
NOTE:
The LH-6 ROM is "free play only". It will not take money to do pay-for-play.
This is the "home version" of the latest commercial release L-5, and includes MANY changes, features, and upgrades. A listing of these is below.
Because of the extra software and features added in this version, the LH-6 ROM revision comes on a larger 8mb ROM chip. It will directly replace the smaller 4mb ROM chip used for previous versions- no circuit board modifications are required.
Changes since commercial version L-5:
New "Ball Save" feature added. This returns the ball to play if it is lost within the first few seconds of play (something not featured in earlier releases of software for this game). This feature can be adjusted from "Off", to anywhere from 1 to 10 seconds time. 3 seconds is the default value.
The timed "5X Playfield" (or "Five Times the Fun") mode now no longer counts down during the animation at the start of multiball. What this means is that if you are stacking (saving) multiball for the "5X Playfield" mode, you won't run down the timer of 5X while waiting for the multiball to start. More fun, more play, bigger points
Score display now shows correct 5X scores for making two, three, four, and five-way combos during "5X" mode.
Bonus Hold feature now works! After collecting Bonus Hold, there will be an extra "held bonus" countdown sequence in the normal bonus countdown at the end of the next ball. If you're on your last ball of the game, you'll get the regular bonus and the held bonus at the same time. Held bonus is added after counting the hazards, boulders, and rafts, but before the bonus is multiplied. So stacking the held bonus with higher multipliers (river classes) gives you bigger points. And River classes (2X, 3X, etc) will now not reset if bonus is held.
New playfield lighting effects added during bonus countdown sequence.
New playfield lighting effects added during start of "Man Overboard"
mode.
Bigfoot now occasionally "sympathizes" with you if you lose your last ball after having a good ball and scoring/playing well.
"Fade out" music added after game over/match sequence. The music plays for a little bit and then "fades out" like later model games do.
Occasional Bigfoot "scream" at game start, or addition of second, third, player, etc.
Occasional Bigfoot "scream" when the last ball drains through one of the outlanes.
High score initials will no longer reset if left/abandoned, and the mode times-out.
Vacation Planner status is no longer displayed during multiball modes.
Delay of about 1 second added to kickout from Lost Mine after No Way Out.
Playfield 10 point switches won't score points before the ball scores a main target or switch.
Bigfoot Hotfoot mode now correctly ends when game is tilted during mode.
Jet bumper values have now been corrected for multi-player games.
Bonus Hold value is now corrected for multi-player games.
Display effects added during bonus count mode.
Bonus Hold award added on successive ramp shots (6, 35, 65, 95).
River Class (bonus X) now no longer resets if bonus is held.
Camera Craze award is now awarded on loop shots.
Boomerang Bend right orbit shot is awarded if a slow ball exits through the Secret Passage. (Boomerang Bend hazard is awarded before Secret Passage is).
Total bonus display is now correctly shown in Status Report.
Bounce Back is correctly lit again at the start of multiball mode, even if Bounce Back is in the process of timing out.
Whirlpool Challenge display effects now show correct state when mode is started a second time during the same ball.
Ball kickback (Bounce Back) is now fired during the standard ball search mode.
Time remaining in modes (including 5X) are now paused while the ball is out of play, and during multiball start display/sound effects.
Grace period added for main multiball. Scoring a Jackpot during re-match will not cancel out the re-match.
Waterfall lights (on top of backbox) will now start again after a tilt occurs.
Game over lighting effects and music (fade-out) added at end of game.