Neptune's Kingdom Slot by Playtech

About as stripped-back as slots get. Three reels, five fixed paylines, and a win lands only when three matching symbols line up in a row from the left. That's it. The green-tailed mermaid sits at the top of the paytable, paying 50x your line bet (the line bet, not the total) for three of her, with the purple-and-gold trident below, then a blue-striped fish, a red lobster and an orange-and-white gold fish. No wild to patch a broken line, no scatter, no bonus round, no free spins.

The one wrinkle is a treasure-chest jackpot. Land three open chests on the fifth payline, with all five lines in play, and you collect a small fixed prize of 100 to 150 coins. That's the ceiling here, and it's a modest one. No point pretending otherwise: this is a simple, dated game with a small top prize and nothing in the way of modern features.

What it has going for it is the return. Over time it gives back more than most slots do, comfortably above average, so a balance tends to stretch further even when the wins stay small. The look is calm rather than flashy: a teal seabed streaked with shifting light, shoals of little fish drifting past the reels, and a bearded, trident-wielding Neptune presiding over the whole underwater scene.