Firstly I will explain the paytable the jackpot for the game is 5000 coins/line bet for 5 captains, 2000 for 5 deep sea divers and 1000 for shark/shark trap. Other symbols included are classic alpha-numeric, submarine and 20,000 leagues substitute.
Now I'll explain why this slot was before its time. It has to have been one of the first games to incorporate not only a substituting symbol but a substituting symbol that also acts as scatter (for free spins).
If this wasn't enough when you delve deep into this wondrous games treasures you can find many re-triggers to help create enormous winnings!
To activate the initial free spins players must have a submarine symbol displayed on the reels at the same time as 20,000 leagues symbol, for every submarine symbol involved you get 10 free spins! This can mean hundreds of free spins if you are very lucky! All free spins winnings are doubled too! The least free spins you can get is 10 spins the most per time is 50! Remember though the more you see during free spins the more free spins you get!
To conclude this review I'd highly recommend this aquatic themed gem from the deep to any player (rookie or experienced). Very underrated in my opinion I give 20,000 Leagues 8/10. Just about flawless!
Can go extremely cold after the big wins take caution with your bet sizing.
Making line wins of 4 or more can be difficult and 5 of a kinds are fairly rare on this game. The fact it goes as low as 9 in the 9-Ace symbols is kind of annoying.
As the game is quite old now (the Next-Gen version alone is now almost 9 years old!) I won't criticize it any longer, as I mentioned in the positive points it was way ahead of its time!