Pondorama!

This expensive piece of kit allows you to take your goldfish out to a fresh water lake and let the little scamp have a wonder around the water-bed, allowing him to meet new friends and expand his horizons in complete safety, with the knowledge that with a touch of a button he'll be on his way back to you, whether he wants to or not.

The Colandarine is a spherical, transparent, plastic vessel with holes covering its surface. It has an array of water jets to propell it through the water in all directions triggered by the pilot's movement inside. A web of sensors built into the sphere detect the goldfish's heading in the water and control the water jets to do the iddy fishy's bidding. At the end of the day a remote signal made by you brings the vessel to the surface where it bobs waiting for you to pick it up. A docking station (read: bucket) is also supplied so Rex isn't put through too much stress from lake to home.

While Rex gets into deep water adventures, you are free to either don your scuba gear and join his exploration, sharing in his joyful sense of discovery, or simply sit back and relax on a small boat, sipping beers, waiting for a bite*, content in the knowledge that now there will be at least one fish that didn't get away.

Artist's impression linked.
Suggestions for a better name would be appreciated.

* (Ensure you take hooks that can't fit through the holes of the Colandarine.)