I wonder what the linear diffusion gradient would look like for that. Like the perforated garden hoses or whatever for soaking soil. Aquatic organisms grow so quick though very curious on the constraints for something like this.

I liked the idea of loading it up on a ship that sails out releasing as it goes out and back. Make it solar powered or even go old school with literal sails.

And it doesn't even need to be a rigid pipe. A flexible pipe made out of, say, waterproof fabric, could be cheaply made to extend miles while remaining open due to the pressure of the water pumped into it.