Simply having full BAB and saves makes Dragon HD pretty good, and there are many things you can do with skills that do not involve hands. Simply Spotting, Listening, Spellcrafting, Bluffing, Hiding, Intimidating... In fact, most skills (and all of the Dunkleosteus's class skills) can absolutely be performed without hands. And it also gives you higher maximum skill ranks if you want to go Truenamer! Aren't you happy? (I'm not even sure truenaming would work underwater, how does that work? What about verbal components?)