I don't think it would be as much of a problem in California as it would be in Florida. My understanding is that your grouper holes are very specific with no particular high spots or landmarks nearby. Out here we go to a kelp bed or to an offshore pinnacle. But after we get there, we hunt failed widely in that general area. If I take a new guy to a spot, it would be pretty easy for him to just glance at a hand held GPS or my boat's GPS to get the numbers.
And then our most prized fish, white sea bass and yellowtail, swim all around the general area rather than being in specific holes. Both fish tend to be on the up-current end of the kelp bed or high spot, but of course that changes with current change anyway. If a guy used this watch to get specific numbers where he shot a fish, the fish might be at the other end of the area an hour later.
Maybe in Norcal where ling cod hang out in holes the watch would be more useful though.