Slots Like Big Fin Bay: How One Expanding Marlin Turns 5,040 Ways Into 117,649
Big Fin Bay comes from Thunderkick, the Stockholm studio behind a run of high-variance releases with a distinctly Nordic sense of humour, and it swaps snow for a sun-warmed fishing bay built around the hunt for a legendary golden marlin. The base game runs on 6 reels with a dynamic row height that starts low and can stretch up to 7 symbols tall, paying across 5,040 fixed ways to win that grow to as many as 117,649 once the bonus reels reach full size. Stakes run from £0.10 to £100 a spin, RTP sits at a single confirmed 96.14% with no reduced build published anywhere, and the 9/10 variance rating backs up a headline win of 15,040x your stake. The two features doing the heavy lifting are an expanding marlin wild that fills its reel and triggers an automatic respin, plus a mystery wild that can turn up to three reels solid gold before your spin is even totalled. Anyone searching for slots like Big Fin Bay is usually after that reel-growth mechanic paired with an actual fishing theme, and there is not a long list of games that manage both convincingly.
Where to Play
18+ only. T&Cs apply. Please gamble responsibly.
How the Game Works
Reviewed by Brian TaylorPublished: July 2026
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The setting is a quiet fishing village rather than a casino floor, with hillside houses stacked above a bay of clear water and a grizzly, pipe-smoking captain watching over the reels. Thunderkick has leaned into a bright, almost storybook art style here, a long way from the darker fantasy work the studio is better known for, and the golden marlin that anchors the wild symbol gets genuine star treatment every time it lands. It is a calmer visual pitch than most high-volatility slots bother with, closer to a summer postcard than a typical bonus-hunter thumbnail.
Under that calm surface the maths is properly spiky. Base spins can run dry for a long stretch since the mystery wild only fires occasionally and the expanding wild needs to land as part of a winning line first, so most of the session is spent waiting rather than winning small amounts steadily. When the reels do start growing during the bonus round the ways count can spike hard within a handful of spins, which is the trade-off you are signing up for with a 9/10 variance rating and a stake range that tops out at £100.
It suits players who already enjoy dynamic-grid slots like Reactoonz but want a gentler theme sitting on top of the volatility, plus anyone who specifically wants a fishing game that is not another Big Bass clone. Casual spinners chasing frequent small wins will probably find it frustrating, but if you are comfortable letting a session run for its bonus rounds rather than its base game, Big Fin Bay rewards that patience more often than most.
Symbols and Paytable
Premium symbols follow the fishing-lodge theme directly: stuffed fish mounted on wooden plaques make up the higher-paying regular symbols, working alongside the golden marlin that only ever appears as part of the wild feature rather than as a standard paying symbol. Lower-value symbols are the usual 9 to A playing cards, styled here as weathered wooden signs to match the bay setting rather than the generic card faces you get on flatter titles. As with most Thunderkick releases, the real payout weight sits with the feature symbols and the way the ways-to-win format multiplies smaller line hits across a growing grid, rather than with any single fixed-symbol payout.
Expanding Wild and Respin
The marlin wild only behaves as a normal wild until it forms part of a winning combination, at which point it expands to cover its entire reel and the game automatically triggers a free respin on that spin. It is the mechanic doing most of the day-to-day work in the base game, since a single expanded reel can turn a modest line hit into a much wider win once the respin plays out.
Mystery Wild
Before any spin is evaluated for wins, up to three reels can be randomly selected and turned fully wild by the mystery feature. It can happen on any base game spin with no symbol needing to land first, which is what stops the base game from feeling completely flat between the bigger expanding-wild moments.
Free Spins and Bonus Game
Landing three or more golden anchor scatters triggers the free spins round, with each scatter worth up to 6 spins and a maximum of 36 spins available on the initial trigger. This is where the dynamic grid starts to matter most, since the bonus is built specifically to let the reel-growth mechanic run.
Reel Growth and Retriggers
During free spins, reels can expand up to a full 7 symbols tall as wilds continue to land, pushing the ways to win from the base 5,040 up toward the maximum of 117,649. Each reel that reaches its full height awards further free spins on top of the original allocation, so a bonus round that starts growing early can genuinely snowball rather than just running out the clock.
Pros and Cons
- Pro: A genuinely different reel-growth mechanic instead of a straight Megaways licence, so it does not feel like every other cascading fishing slot on the market.
- Pro: Max win of 15,040x stake is a serious ceiling for a £0.10 minimum bet, giving low rollers a real shot at a life-changing multiplier.
- Pro: The mystery wild keeps base game spins interesting without needing a scatter to land first.
- Pro: Bright, warm art direction that stands out from Thunderkick’s usual darker catalogue.
- Con: High volatility means long dry spells are normal, and the base game alone rarely produces meaningful wins.
- Con: A single confirmed RTP build means there is no lower-volatility or boosted-RTP version to fall back on at different operators.
- Con: Retrigger chains rely on reels reaching full height, so a slow-growing bonus round can end quickly and underwhelm.
Game Screenshot
Big Fin Bay base game, showing the 6-reel layout and 5,040 ways to win.
Demo Play
Big Fin Bay is widely available in free demo mode through most UK-facing casino lobbies that carry the Thunderkick catalogue, running on the same 96.14% RTP build as the real-money version. It is a sensible way to see how often the mystery wild and expanding wild actually land before committing a bankroll, given how much of the game’s output depends on those two features rather than base-game line hits.
Expert Take
Big Fin Bay earns its place as one of Thunderkick’s more interesting recent releases mainly because it resists the temptation to just badge itself as a Megaways clone. The reel-growth system is genuinely the studio’s own, the theme is a welcome change of pace from the usual demon-and-dungeon Thunderkick house style, and the 15,040x ceiling is competitive without needing an inflated coin-value trick to get there. The trade-off is a base game that can feel thin between features, so this is one to play with a session bankroll set aside for the bonus rather than one expecting steady base-game returns.
Similar Slots to Try
The original Blueprint fishing slot, a simpler 5-reel format without the growing-grid mechanic.
Fixed 5,040 ways too, but built around a collecting fish-value meter instead of expanding reels.
Another Push Gaming ocean title with punishing volatility, though it sticks to a standard 5×3 grid.
The closest ways-count comparison, running a licensed Megaways engine rather than Thunderkick’s own system.
Keeps the lakeside angling theme but trades the growing ways count for ten fixed lines and a shared progressive crown chase.
About the Developer
Thunderkick was founded in 2012 and is based in Stockholm, with an 80-plus person team working out of the same office. The studio holds licences from the UK Gambling Commission, Sweden’s Spelinspektionen, the Malta Gaming Authority and Ontario’s AGCO among others, and remains an independent developer, it has not been folded into a larger group the way Microgaming became Games Global or NetEnt became part of Evolution. That independence shows in the catalogue, which leans toward smaller numbers of carefully finished games rather than a rapid release schedule.
An older Thunderkick title with a similar high-variance, feature-led structure.
Another wild-driven Thunderkick game, built around a shifting multiplier instead of reel growth.
One of Thunderkick’s better-known cluster-pay titles, sharing the studio’s taste for unusual grid mechanics.
A newer Thunderkick release showing the same wild-heavy, feature-first design philosophy.
Big Fin Bay Key Stats
Big Fin Bay slot information last reviewed: July 2026
| Big Fin Bay Slot Info | |
|---|---|
| Name: | Big Fin Bay |
| Provider: | Thunderkick |
| Developer Rank: | Estimated top 15 out of 90+ Thunderkick games |
| RTP: | 96.14% (single confirmed build, no reduced-RTP variant published) |
| RTP Category: | Medium-High |
| RTP Rank: | Above UK average |
| Feature Description: | Expanding Wild, Mystery Wild, Free Spins Feature, Expanding Reels, Retriggers. |
| Feature Categories: | Free Spins, Expanding Wilds, Reel Modifiers |
| Reels: | 6 |
| Rows: | Dynamic, 2 to 7 |
| Paylines: | 5,040 ways (base game), up to 117,649 ways (bonus game) |
| Volatility: | High |
| Volatility Rank: | High (9/10 on Thunderkick’s own scale) |
| Min Bet: | £0.10 |
| Max Bet: | £100 |
| Max Win: | 15,040x stake |
| Release Date: | 31 March 2021 |
| Slotslike Rank: | 612 out of 4,200+ games (View Top 100) |
Slots with the Same Features
Another Thunderkick title where a multiplier mechanic builds through the bonus rather than resetting each spin.
Shares the expanding-wild-into-respin structure, though its multiplier never resets between hits.
A fishing theme with its own progressive meter feature instead of a growing reel grid.
Uses block symbols to expand win potential, a different route to the same “reels get bigger” appeal.
Frequently Asked Questions
How does the expanding wild work in Big Fin Bay?
The marlin wild only expands after it lands as part of a winning combination. Once that happens it fills the whole reel and the game runs an automatic respin on that reel.
What is the RTP of Big Fin Bay?
96.14%. It is the only RTP figure Thunderkick or any independent reviewer has published for this game, so there is no reduced build to watch out for at specific operators.
What is the maximum win on Big Fin Bay?
15,040x your stake, reached when the bonus reels grow to full height and the ways to win climb toward the 117,649 maximum.
Is Big Fin Bay high volatility?
Yes. Thunderkick rates it 9/10 on their own variance scale, and the base game backs that up with long gaps between meaningful wins outside the bonus round.
What are the best slots like Big Fin Bay?
Big Catch Bass Fishing Megaways is the closest match on ways-to-win scale, since both slots grow well past 100,000 ways during their bonus rounds. Fishin Frenzy and Big Bass Bonanza cover the fishing theme without the expanding grid, while Razor Shark matches the volatility with a standard reel layout instead.
Can I play Big Fin Bay for free?
Yes, a free demo running on the same 96.14% RTP build is available through most UK-facing casino sites that carry Thunderkick’s catalogue.
Who makes Big Fin Bay?
Thunderkick, an independent studio founded in Stockholm in 2012 and licensed by the UK Gambling Commission, Spelinspektionen, the Malta Gaming Authority and AGCO.
Our Verdict on Big Fin Bay
Big Fin Bay stands out because Thunderkick built its own reel-growth system instead of licensing Megaways, and the fishing-village setting gives the studio a lighter, warmer visual register than most of its back catalogue. The 15,040x ceiling and 5,040-to-117,649 ways swing are the real draw, but they come wrapped in a base game that can go quiet for long stretches between the mystery wild and expanding wild doing their work. It rewards patience and a bankroll set aside for bonus rounds rather than one expecting steady base-game returns.
SlotsLike rating: 8/10