Here are some pictures of the latest AMOS version (perhaps to be called "Mini AMOS"). It uses the same electronics boxes as the regular AMOS, except it only uses a 4 foot long bodyboard, doesn't have a solar panel, and uses a water propeller instead of the air propeller on the standard robot. The board shown below doesn't have a survey-grade GPS antenna (just uses a GPS / USB stick), but that could be added later if desired. As it stands right now, its weight is only 4.5 kg.
There will need to be some minor software modifications to drive and control the water propeller, but these should be relatively minor. It will be interesting to see how fast it can go, and / or what kind of performance it has in wind, waves, currents, etc.