First I’d like to state that ICOM makes great products and I own four of their radios.
The M93D is a bit bigger than the M1V, which I have used with a shoulder mount without any issues, so it’s probably workable from a size perspective.
My one concern is the whether the “float and flash” feature can be unintentionally activated by splashing water or momentary immersion, such as when rolling, punching through surf, etc. If so, that would be a problem, not only because of the annoyance of the flashing light, but because it automatically switches to “Man Overboard distress call mode”. It’s not clear whether that affects your ability to use the radio for normal communication or not.
If this is an issue, it means that you’d have to carry it in a waterproof bag, which would compromise functionality in situations of real need. More research needs to be done. I suggest either downloading the owner’s manual or calling ICOM and asking them for more information.