Calipso

There’s no need to fear the siren's song in Calipso, the mermaid-themed slot from ThunderSpin. This feature-packed affair offers unlimited free spins with a maximum win multiplier of 8x, a cash bonus game, and easy, charming design.

Theme

In ThunderSpin’ world, there’s more to the ocean floor than meets the eye: the reels are set before a sunken city resembling the famed Atlantis. Massive columns and caverns are all around, and sharks swim behind the gaming action.

Gaming symbols include a variety of undersea life, such as mollusks, star fish, seahorses, and oysters containing pearls. A fish symbol acts as wild, while an elegant red box, decorated with pearls, acts as scatter, triggering the sunken treasure bonus game. The mermaid Calypso acts as stacked scatter, opening the free spin feature.

The flute-heavy, upbeat sound design keeps spirits up even below sea level. Lower-value symbols are provided by the playing card values ace through jack.

Betting Options and Functions

ThunderSpin is a subsidiary of the Malta-based company BOSS., which offers complete casino packages to its clients. Though not a fully independent designer, however, ThunderSpin delivers consistently excellent games on par with anything coming out of industry giants such as Microgaming or NetEnt.

The underwater realm of Calipso has been designed with every detail well attended to. There are 21 paylines, all paying from left to right. Bet level is adjustable from 1–10, with coin value adjustable from 0.01–1.00 for an overall per-spin bet range of 0.21–210.00 times the betting currency.

Autoplay is available for up to 500 spins, with optional win and loss limits if the feature is engaged through the settings menu, which also allows players to adjust sound and image options, as well as quickspin. The overall theoretical return to player ratio is below-average at 95.8%.

Features

There are plenty of fish in the sea, and in Calipso, plenty of features as well. In the sunken treasure bonus game, players look for gold in the pieces of a sunken galleon. Each find awards a cash prize of 2-5 times the bet size. The feature ends when a searched compartment comes up empty, releasing air bubbles.

A free spin features is also included, triggered by the stacked mermaid symbol. Once the feature begins, a pearl- and crown-bearing fish symbol is added to the reels, acting as free spin scatter. This is the key to increasing win multipliers during the feature. 5 collected symbols raise the win multiplier to 4x; 15 raise it to 6x; and 20 raise it to the maximum of 8x. Each free spin scatter symbol also adds 3 free spins to the total.

Our Take

Calipso offers a great deal of what modern slot players crave: sharp graphics, elegant design, and excellent bonus features. The only blemish is its low RTP, which is no small matters. Another underwater slot by AGames, Gold Sea, has a similar structure, but higher RTP.