Fast Moving Water
You know it when you feel it
What makes a startup grow fast?
I've worked with companies like Wispr Flow, Replit, and GPTZero during hyper-growth — and others, just as well run, that grew far more slowly.
What explains the difference still surprises me.
The biggest driver is rarely marketing, sales, or really any function.
It’s the startup’s space.
Fast-growing startups are in fast-moving water.
If your market doubles each year, you’ll probably also double each year. Before you’ve done a single thing well.
Why now
I frequently hear from founders who feel stuck on this problem.
They feel they’ve chosen a swimlane and regret that it’s in slow-moving water. No matter how well they execute, growth is slow.
Over time they even start quietly disliking their company, looking for ways out.
Meanwhile, these founders can’t help but notice startups in fast-moving water who seem to win regardless of how they execute.
But it’s much easier to switch swimlane now than ever. Just a few years ago, up-front R&D costs meant that switching swimlanes might be prohibitively expensive.
It used to be the case that so much of whether a startup would succeed was sheer luck: “being in the right place at the right time”.
But now it’s cheaper to build than ever. So startups should be more willing than ever to seek out fast-moving water.
Adjusting space is a controllable process just like any other aspect of running a startup.
60:40
There’s a parallel I keep coming back to. Human personalities are influenced something like 60:40, nature versus nurture. Genes shape us more than environment, and of course, we’re stuck with the genes we’ve got.
I suspect startups work in roughly the same way. In terms of eventual growth, space is 60% and everything else combined is 40%.
But unlike genes, you’re not stuck with your space1.
Your space is (a) choosable up front and (b) editable as you go.
Choose up front
Many founders barely consider space when they start a company.
I suspect this is because they’re excited to get to work, tackling a meaningful problem that feels big enough.
Often this is combined with some form of early pressure — a looming YC demo day, launch expectations, a desire to get out ahead of a competitor, tight finances, and so on.
Carelessly choosing space in a week can create years of regret.
Founders should ask: is the market exploding?
In more detail, is there some reliable outside force rapidly driving a sustained increase in demand?
Writing this feels almost banal in how obvious it is. And yet I still see thousands of founders toiling in spaces that are slow-growing, flat, or even shrinking. Clearly the topic receives far less than its fair share of attention.
What are some examples of choosing well up front?
A startup I’ve advised for over a year, GPTZero, builds the world’s leading AI text detector. The explosion of AI provides epic tailwinds. Each month there is dramatically more AI text. More AI text demands more AI detection. With no sign of slowing.
Another, Wispr Flow, builds the best voice-to-text imaginable. This one’s interesting as voice to text isn’t new — I remember when a Dragon NaturallySpeaking dictaphone showed up in my house in the 1990s.
But the space is exploding. Not because dramatically more people are communicating online (though that’s directionally true). The strongest tailwind is an uptick in people talking to AI. We ramble at Claude. Developers prompt Cursor. Lawyers mutter to Harvey. This trend makes Wispr Flow a must-have and, again, has no sign of slowing.
Edit as you go
Just as founders should consider their space up front, they should frequently revisit their space.
But most struggle with this.
The first hurdle is that founders assume space is a one-time decision made early in the company’s life. That it’s impossible to revisit later on.
Of course, by the time you have a product, customers, and a reputation, shifting focus can be challenging. I recently described the challenges of embarking on Act 2.
But this is status quo bias. The switching costs are rarely bigger than the opportunity cost of missing out entirely.
Even if founders agree that it’s wise to routinely revisit space, the second hurdle is actually having enough time to drive change.
Adjusting space typically requires founder-level drive.
But most founders end up bogged down running the current business.
Meanwhile, other team members end up with their heads buried in the sand. The reason is obvious: company success (not to mention everyone’s livelihood) depends on avoiding distractions.
The best founders clear both hurdles.
They know that space should be frequently revisited. And they make time to do it.
Examples of startups successfully switching swimlanes are everywhere2.
Replit was founded in 2016. They spent 9 years cycling through product angles and business models. In late 2024 they fully reoriented around the fast-moving water of AI coding agents. This ended an almost decade-long grind, jumping to hundreds of millions in ARR in under a year.
Superpower started in blood tests, but is gearing up to shift towards peptides. While blood testing is lucrative — Function Health reached $100M in ARR in just a few years — peptides are several orders of magnitude faster moving.
Bigness
A common pitfall I see is simply reaching for big markets. But it doesn’t matter if a market is big to begin with.
In fact, bigness may even be an anti-signal.
A large market de-risks the opportunity — you know it's big enough. But it adds a new risk: that the market stalls or shrinks.
I’d pick a small but exploding market over a big but flat one any day.
Evenings and weekends
Founders typically know what space adjustments might bring them closer to fast-moving water.
But to add inspiration, my favorite shortcut is to ask: what are the smartest people you know spending evenings and weekends on?
What excites them enough to spend spare time on are likely spaces that are about to explode3.
Paul Graham defined a startup by its growth. But where does that growth come from?
The usual answers are tactical: aha moments, smile curves, network effects; automation and arbitrage; product adjustments and GTM execution.
I think it comes from something upstream of all of these: the water you choose, and the water you’re willing to switch into.
Next time you dig into growth, ask: are you in the right space?
I know this analogy won’t age well.
Is switching swimlane the same as a Lean Startup pivot? Similar. A pivot is usually in response to something failing. Startups can seek fast-moving water even when they’re winning, i.e. shifting from a decent market into an excellent one.
Running my own test, what are the smartest people I know spending evenings and weekends on? Right now: peptides, psychedelics, looksmaxxing, longevity, human-computer interfaces, agentic economy, anything but traditional schooling. Ask me again in a year and I’m sure the list will have moved.
Epic. Obvious but good reminder. Sharing with my team!