Sillwater: Seed round

Sillwater is a flood-risk company for commercial insurers. Flood maps are drawn for whole neighborhoods, but a flood reaches one building at a time. Sillwater gives every commercial building its own risk score, so an insurer can price the water that is actually coming. This deck covers the gap in today's pricing, the proof that scoring by building works, and what a $4.5M seed round will fund.

Insurers price flood by zone map because the map is all they have. We reviewed 4,800 flood claims from partner insurers between 2021 and 2025. Of every 100 losses, 61 happened inside a mapped flood zone and 39 happened outside one, where the map showed no special risk. Nearly four in ten flood losses were never priced for.

Flood risk belongs to the building, not the zone. The same storm can flood one warehouse and spare the one next door. Street-level elevation, drainage and basements decide which, and a zone map can see none of them. To price flood properly, you have to score every building on its own.

Sillwater runs a four-step loop for every building. It surveys elevation, drainage and basement data; simulates thousands of storms against the building; prices the result as one score and a premium range an underwriter can read; and learns from each paid claim. Today the system serves 2.4M building scores a month.

A flood zone map is drawn for whole neighborhoods, is redrawn every few years, and gives one answer: in the zone or out. A Sillwater score is calculated for each building, is refreshed as claims and data arrive, and gives a risk number an underwriter can price.

Six insurers priced flood by building for twelve months, and every one paid out less. Their flood loss ratio, the share of premium paid out in claims, fell from 71% to 58%, a drop of 13 points. As one chief underwriting officer put it, they stopped arguing about the map and started pricing the building.

Annual recurring revenue is $1.2M today and has grown 18% a month for eight months, nearly quadrupling in that time. Only today's figure is reported; the earlier months are implied from the growth rate. Behind the curve are 19 paying insurers, and existing customers spend more each year, shown as 128% net revenue retention.

Unit economics are healthy. Gross margin is 81%, after software and data costs. Sales spend pays back in seven months on average across all 19 customers. And no customer has been lost since launch, so every new insurer adds revenue that stays.

Insurers spend about $2.6B a year on flood-risk analytics, and $650M of that sits with mid-size insurers, the customers Sillwater serves today. That is a quarter of the market. At $1.2M in annual recurring revenue, Sillwater is a dot inside that ring, drawn to scale. These market sizes are company estimates.

The plan has four milestones on a real calendar. Today Sillwater has 19 customers and $1.2M in recurring revenue. Coverage of the Gulf and Atlantic coasts goes live in the first quarter of 2027, the underwriting workbench ships in the third quarter, and by the fourth quarter the goal is 60 customers and $4M in recurring revenue.

Sillwater has three founders. Mara Voss, the CEO, priced catastrophe risk at a reinsurer. Idris Calder, the CTO, built flood-forecast data systems at a national weather agency. Noor Whitfield, the chief scientist, is a hydrologist who models how water moves through streets and basements.

Sillwater is raising a $4.5M seed round. It funds two things: coverage on the Gulf and Atlantic coasts, and the underwriting workbench customers keep asking for. Reaching $4M in annual recurring revenue by the fourth quarter of 2027 needs about 10.6% growth a month, well below the 18% Sillwater is compounding at today.