Here's what I wrote in part of the Kickstarter update that enplanes it.
We had built several early prototypes of the buoy design toward the beginning of the project, and were intrigued by the possibilities. But after further testing, we realized that making the WiFi Topside also a towable buoy would add a large amount of risk to the functionality and development of the system as a whole. To keep the buoy from being towed beneath the surface, it would need to be fairly large (nearly the length of Trident itself), to make it self-righting, it would need a large keel ballast which would increase its displacement and add a lot of drag, and finally, to make sure people wouldn’t lose the system, we’d need to do extensive development work with the antenna and radio to assure a solid connection and develop a return-to-home feature if the vehicle lost signal far from shore.
While all of these features could have been designed, they would add months to the development process and could reduce the reliability of the system. We decided to stick with a simpler design that we knew we could trust. The new topside module is something we are very proud of. It is simple and robust, and makes the system a lot more transportable due to its shape and size. Although it is not a floating buoy, it’s still designed to be waterproof and positively buoyant so if it falls overboard accidentally, the system won’t be lost. Though not hydrodynamic, users on the water who (at their own risk) want to decouple the buoy from their boat may still be able to experiment with putting the buoy on other floating devices. A wifi buoy is just one of the possibilities for the modular, smaller design. We’ve talked with a few people about the new design, and have already heard several ideas of how folks will be adapting it to their specific purpose.
A big perk of the new Topside design is that it is now small enough to be attached to the hub of a tether reel, which will make tether management much more elegant for people who ordered a 100m length of tether. The image below shows a 3D printed prototype of the WiFi Topside Module (we’re still waiting for the nicer prototypes to come in) attached to a tether reel. This configuration allows the reel to be used without a slip-ring because the WiFi Topside can just rotate with the tether.
Hopefully this helps explain the change. Please feel free to post if you have any other questions or ideas!