Swimming and water activities are major features of worlds like Sulani and Gibbi Point, so having those features stop working is disappointing and frustrating.
For anyone still experiencing this, there is an official EA bug report thread tracking the issue here:
https://forums.ea.com/idea/the-sims-4-bug-reports-en/no-swim-in-ocean-option/13275164/comments/13352624
If you are able, please consider voting on the report, adding a comment to the bug report, and sharing a save file with EA. The more examples EA receives, the easier it will be for them to investigate and reproduce the problem.
When commenting, helpful details to include are:
• Game version and platform
• Whether you have mods/CC installed
• Whether the issue occurs in a new save
• Which worlds or water areas are affected
• What happens when you try to swim or use watercraft
• Whether NPC Sims are also unable to swim or use watercraft
Thank you, and I hope this helps!