Host a Waterpark Simulator co-op session by choosing a new or existing park in the current 1.0 multiplayer interface, then inviting up to three other players through the options the live Steam build presents. CayPlay confirms both new and existing parks, a four-player total, and optional proximity voice. The exact button sequence is not stated because it was not captured in the audit.
For an existing park, back up first. The official release notes do not define save ownership, client persistence, host migration, or what happens to uncommitted work after a disconnect.
Prepare the park and players
Make sure everyone is launching the Steam base game with AppID 3293260 on the current public branch. Do not mix the separate Demo AppID 3730180 into a base-game session.
Decide whether to create a disposable test park or use an existing save. A test park is best for learning the lobby and permissions. If the existing park matters, close the game and copy its files outside the live save folder using the official save procedure.
Agree on the session goal and on who can make major purchases, demolish buildings, expand, or accept optional quest choices. This is a social safeguard; the official notes do not document permission locks for those actions.
Open the current multiplayer flow
Launch Waterpark Simulator through Steam and use the multiplayer option visible in version 1.0. Select the intended new or existing park and follow the current host or invite controls. Invite no more than three additional players, matching CayPlay’s documented limit.
Confirm that every guest reaches the correct park before opening for business. If someone lands in a different state or cannot join, stop and record the message rather than repeatedly changing settings.
Do not present an older pre-release lobby screenshot as current. The feature launched with 1.0 on July 31, 2026, so the live build’s wording wins.
Run a five-minute permissions test
Before a large project, ask each client to perform one low-risk action that their planned role requires. Test movement, interaction, a small permitted build or service action, and communication.
Observe which actions persist in the shared park. Do not infer a general rule from one action; building, spending, inventory, and achievement tracking may have different behavior.
If the group wants achievements, choose one simple visible condition and see whose Steam profile advances. No universal host/client achievement rule is claimed here.
Configure communication for park size
Proximity voice is optional and suits players working near each other. Confirm that all participants want it enabled and that microphone settings behave as expected.
For distant work, CayPlay says walkie-talkies communicate across the map when equipped by the relevant players. The megaphone is another released multiplayer communication tool. Test the current range and behavior rather than assuming it matches proximity voice.
Keep a text fallback available. If one player cannot hear others, distinguish a microphone or privacy problem from the distance rules of the selected in-game tool.
Assign roles without assuming locked permissions
One useful starting split is construction and spending, guest service, cleaning and repair, and safety or circulation. Rotate when necessary and announce major changes.
The split reduces duplicate work, but it is not a game-enforced permission model. CayPlay has not publicly documented a role-lock system in the sources reviewed.
Remember that the spray can is disabled in multiplayer according to the 1.0 notes. A missing spray-can action is expected co-op behavior, not automatically a client bug.
Save and exit deliberately
After the test actions, save through the supported game flow and exit normally. Have the original host reopen the park and verify that the expected changes remain before beginning a long session.
This test does not prove who owns progress in every case. It simply checks the selected park and current public build. Keep the pre-session backup until the group has confirmed the result.
If the host disconnects unexpectedly, stop large changes and record the remaining session state. Do not promise host migration or automatic recovery; those behaviors remain unverified.
Diagnose joining failures
Confirm every participant owns and launches the base game, is on the public branch, and is using Steam online features. Recreate the invite once from the current host interface.
Record the host, affected player, time, visible error, whether a new and existing park behave differently, and whether other players can join. This separates a single account or network issue from a session-wide problem.
Avoid generic router changes, firewall exceptions, or port forwarding unless CayPlay or Steam provides a game-specific reason. Use Steam discussions or CayPlay support with the evidence you collected.
Hosting answers
Can I host more than three guests?
The official limit is the host plus up to three other people. No larger player count is established.
Should I host my main park first?
A disposable new park is safer for the first permissions and persistence test. If you use the main park, back it up.
Will clients keep the park?
Save ownership and client persistence are not documented by the official launch notes. Test on a noncritical park and avoid stating a rule until verified.
Can Steam players invite console players?
Cross-play is unverified. Console availability is not proof of Steam-console matchmaking.
What voice tools are confirmed?
Optional proximity voice, walkie-talkies, and a megaphone are confirmed. A trumpet is also listed as a multiplayer tool.
Sources checked 2026-08-02: Waterpark Simulator Steam page and CayPlay’s official 1.0 announcement feed.