Join a magical mermaid deep beneath the waves in Siren’s Kingdom. This 5 reel, 30 payline slot from Iron Dog Studio comes with expanding wilds that fill whole reels and a bonus round that up to 36 free spins. Look out there for sticky wilds that expand to fill 2 adjacent positions before swimming away. Dive in, on all devices, from between 30p and £150 per spin.

Siren’s Kingdom is a lovely looking slot – set on the ocean floor, the reels include A to 10 playing cards alongside an assortment of starfish and shells that are embellished with pearls. The best of them pays 13.33 times your stake if you land 5 on the same payline.

The flame-haired siren is the game’s wild which only appears on the top position of the reels – she substitutes for all other symbols apart from the scatter and expands to fill the whole reel whenever she hits in the base game. It’s possible to land multiple siren wilds on the same spin which result in multiple wild reels.

The main feature is the Free Spins feature which is triggered by landing 3, 4 or 5 of the scatter (the octopus holding the pearl). You can then look forward to 14, 25 or 36 free spins. The wilds are a little different during the feature though.

The wild doesn’t expand when it hits – instead, it locks in place for the free spin that follows. It will also fill 2 adjacent symbols for that free spin before disappearing. Landing multiple single wilds on the same free spin can quickly fill the reels with wilds on the next free spin with potentially exciting results.

We really enjoyed Siren’s Kingdom – it’s a very simple game but the generous allocation of free spins and the wild extras make it a very playable one. There’s a magical feel to the visuals here which are complemented by a sweeping orchestral backing track. It’s all rather lovely.

Many slots bombard the senses with in your face imagery and intrusive sound. This is far more understated and all the better for it.  Don’t mistake understated for boring though as the expanding wilds and Free Spins feature offer plenty of potential – there’s up to 1,000 times your stake to be won on every spin/free spin.

There are loads of underwater themed slots to choose from already. Siren’s Kingdom shows there’s always room for more if it matches classy design with punchy features. Additionally, you could go diving for riches with Play ‘N Go’s Mermaid’s Diamond and Playtech’s Great Blue Jackpot which are both highly volatile.