Mermaids Millions is one of those online slot games that never seems to go out of fashion.

It's easy to play, virtually free of complex animation and bonus features, and can be played at a range of stakes.

In fact, so popular is this watery video slot, Microgaming launched a multiplayer version of the game where all players taking part could benefit from the bonus rewards.

Let's take a closer look at the secret of Mermaids Millions' longevity.

Mermaids Millions slots highlights

Developer: Microgaming
Paylines: 15
Reels: 5
Rows: 3
Min. Bet: 0.01
Max Bet: 75.00
RTP: 96.56%
Top features: Free spins, wild symbol, pick 'em bonus

Classic Microgaming slots fun under the sea

Dozens of new online slots hit the market every year, some fall by the wayside while others become fan favourites. And just because a video slot is showing its age, it doesn't mean it should be completely discarded.

When it comes to Microgaming, there are some games that seem to weather the ageing process better than others. Thunderstruck and Thunderstruck II are still played online, despite their limited number of paylines and bonus features.

Joining the pile of Microgaming classics is Mermaids Millions.

It's now 10 years since the underwater-themed slot was released at Microgaming casinos. There is no six-page paytable to confuse the player, just a couple of very simple bonuses and some jackpots to match.

Play 15 paylines from 0.01 a coin

Like many of Microgaming's older slots, Mermaids Millions features 15 adjustable paylines. Stakes are set using the Select Coins button, and there's even an Expert mode that lets the player adjust the Autoplay.

The low payouts are reserved for the royal symbols - 10, J, Q, K, and A. Hitting 3-5 10 or J symbols pays out between two and 75 coins. The Q and K pay between five and 100 coins, while the A pays 10-125 coins.

The high-paying symbols are represented by iconic images from the mermaid's world. The seahorse pays 15-250 coins for three or five of a kind, while the giant clam and jewel box pay 20-500 and 50-500 coins respectively.

Trigger free spins or a Treasure Bonus

There is a high-paying wild symbol in Mermaids Millions.

It's the chief merman and he will substitute for all symbols except the scatters when he appears. You'll only need two wilds to earn coins (five in total), while three, four, and five wilds pays 200, 2,000, and 7,500 coins.

Look out for the mermaid scatter. As well as winning the player cash prizes when two or more land anywhere on the reels (two coins for two scatters up to 400 coins for five scatters), the mermaid will also trigger free spins.

Three, four or five mermaid scatters activates 10 free spins. All wins are tripled during the feature, and the bonus can be retriggered.

Finally, three or more treasure chests will activate a cool pick 'em-style bonus feature. A second screen appears, filled with treasure chests. Simply pick from the chests on-screen in order to reveal cash prizes or multipliers.

Play Mermaids Millions for free at Betway Casino

Mermaids Millions, like Thunderstruck, is a regular winner with slot players.

While its graphics and gameplay may be getting a little dated, the RTP and low volatility makes it a winner with players. And that's not to mention the two bonus features that have real potential for decent prizes.

Check out the Betway Casino slots lobby and open up Mermaids Millions today for some underwater thrills.

Don't forget, Betway Casino also offers a Multiplayer version of the game, allowing up to six players to play the slot at the same time.

If one player triggers a bonus feature, all players linked up get to enjoy the spoils. It's another reason to check out the Microgaming classic.