Web App

Tidepool

An offline-first tide and weather planner for small-boat sailors, built as an installable progressive web app.

Live Demo

Placeholder preview of the Tidepool interface

Project data

Role: Solo developer
Type: Web App
Stack: SvelteKit
TypeScript
IndexedDB
Workbox
Duration: 3 months
Year: 2025
Status: Live
Links: Demo Repository

The challenge

No signal at sea

Sailors plan trips in the harbour and check them again on the water, where the connection disappears. Existing apps showed spinners exactly when people needed the data most.

Tidepool had to work fully offline for a week of planned trips and still feel instant on old phones.

How it was built

Development process

Six phases from the first conversation to the release. The bar shows how the time was split.

7 weeks in total

Research
Sailors walked us through planning a trip with no signal on board; the offline cases came straight from them.
3 days · Offline scenarios
Architecture
Data model, rendering strategy and API contracts were agreed before the first screen was drawn.
4 days · ADR, data model
Interface
A component inventory and responsive layouts, built entirely from design tokens.
1 week · Token set, component inventory
Build
Features went live in small slices behind flags, with typed boundaries between client and server.
3 weeks · Feature slices
Testing
Unit, end-to-end and accessibility checks ran on every pull request.
1 week · Test suite in CI
Deployment
Every branch got a preview environment; the production rollout was a single click.
3 days · Preview and release pipeline
Result
Used on more than 1,200 trips in its first season with zero reported data loss.
Open the live demo

Screens

Outcome

The results

What changed after launch

Used on more than 1,200 trips in its first season with zero reported data loss.

SvelteKit
TypeScript
IndexedDB
Workbox

Key figures

Offline score: 100
JS shipped: 40 kB
Store rating: 4.8

Under the hood

Offline as the default state

The service worker precaches the shell and stores every planned trip as a self-contained bundle. The UI reads only from local storage, so online and offline look identical.

Forecast updates are diffed on the server and shipped as small patches, which keeps background syncs under 20 kB.