On my various devices...
Roku Ultra 4660x - Aquatic Life v.13.0.90000013 - available as screensaver, no seperate channel/app ever seen on home screen for me.
Insignia RokuTV - Aquatic Life v.3.0 build 9000013 - available both as screensaver and channel/app.
Roku Express 4k+ - Aquatic Life v.3.0 build 9000013 - available both as screensaver and channel/app.
Roku Premiere 3920 - Aquatic Life v.3.0 build 9000013 - available both as screensaver and channel/app.
I believe I was mistaken about being able to search on the Ultra for Aquatic Life. Looks like the previous thread posted in the Community before has it correct. Aquatic Life v13 is screensaver only. (also won't yield Search). Aquatic Life v3 is both screensaver and channel/app.
[The above is what I am seeing on my devices and Ultra 4660x OS 11.5 build 4312-46]
I certainly won't argue if others have seen a seperate channel/app on their 4660 devices, but was never present for me as a standalone channel/app on mine.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102