No the ice ducers are not the best when moving. Marcum sells a "fast" open water ducer, ($200) but I already have a HB688. The HB doesn't have near the target separation as the LX7. I have used them side by side when ice fishing. So when stopped I plan to throw the LX7 ducer overboard.
The photo is the Scotty 140, they have others, these are made for the kayaks. This is $20 on Amazon, can't go wrong, but I do need to measure the distance from boat to water line before ordering.
Thanks for posting pics Mealworm. I want to find some way to drape it over the side without damaging it. Drilling them holes in it would scare me...