JSEM TU! is available on Google Play from today

JSEM TU!, the app for cold-water swimmers, has been available to download from Google Play since 4 September 2026. We updated this article on 12 September to reflect the current version. It is in public open testing in Czechia and Slovakia. Accounts can now be created from age 9; anyone under 16 needs a parent or legal guardian's approval before using the app.

JSEM TU! is a Czech app built on the experience of a real cold-water swimming group. But it is not just for swimmers. It is ready for the new winter swimming season, and the same approach can help running, exercise, hiking and other groups that meet regularly.

Starting with cold-water swimmers

Cold-water swimming is the app's first fully developed specialism. JSEM TU! brings together two things we needed ourselves: organising a real group by the water and keeping a personal Cold-Water Diary.

• Group swims and dips: the organiser sets the location, season, days and times. Members can see when the group is meeting and confirm “I'm here” when they are at the right location.
• Regular attendance: the app records attendance and shows an overview and rankings for the whole group. The aim is to encourage people to keep coming back, rather than set records in icy water.
• Cold-Water Diary: record cold showers, baths or tubs, and outdoor swims as separate types of activity. Entries can include water and air temperature, time in the water, distance swum, location, how you felt, a note and a photo.
• Charts and statistics: view temperatures, time and other measures over a chosen period, and compare a new entry with your previous session of the same type.
• Sharing and your own data: create a social media image from selected statistics, a chart and your own photos. Export entries as XLS, CSV, TSV or JSON.

The entire app, including the Cold-Water Diary, requires an internet connection. Local caching is not a substitute for an offline mode.

Running, exercise and other group activities

JSEM TU!'s core features are not tied to cold water. They can help wherever people meet regularly at a particular place and time: running, exercise, fitness, hiking, cycling, swimming, team sports, volunteering and other community activities.

An administrator creates a public or hidden activity, adds its location, season and schedule, and can invite other administrators. Participants find the group, join it and check in at the venue. Everyone then has up-to-date information, the member list and attendance records in one place, without having to search through several chats and spreadsheets.

Screenshots of the app

The following screenshots show the actual app when this article was published on 4 September 2026. They cover the community features and Cold-Water Diary; the layout of the controls may differ in newer versions.

Click an image to enlarge it.

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How parental approval works

When registering a child, enter their correct date of birth, the parent's name and the parent's own email address. The parent opens the link in the email, reviews the details and documents, and approves or declines the request. The child then completes registration by following the instructions. Entering a parent's email address, or signing in with Google, does not in itself provide parental consent. See the questions and answers for details.

Who can download it?

Public testing means the app is already available through Google Play, while development continues and real users' experiences help shape it. If you find a bug or have an idea for an improvement, let us know. That is what testing is for.

Download JSEM TU! now

If you use Android, open the app's Google Play listing and select Install. Accounts are available from age 9, with parental approval required for users under 16. For more information, detailed descriptions of the features and guides, visit the official app website.

See you by the water — and at our other group activities,
Otakar Zemek