Yes, Destyn was justly concerned that his fingers might be caught by the crab's "pinchies", but this was simply a sacrifice which had to be made for the greater good, which is to say, dinner.
"Fear not, you will simply need to snatch with great speed and skill. The cra- the buggies have arms for pinching on the sides, yes? Well, let me tell you, I am an experienced warrior and their weakness is their own armor. For though they can attack you if you grab them from the side or the front, they can only reach there- if you snatch them by the leg or back, then they will be unable to pinch you however they might struggle."
Indeed, this was the moment that all of her years of faithful training had surely led to. Doubtless each of the old Sunsinger masters would be beaming now, basking in fulfilment of purpose to know that their techniques and advice and patient correction had led to Imogen on the beach, tying up a fae'thalen lad and giving him tips on how to grab crabs.
The witch paused for only a moment in her work, when Destyn mentioned horses. That... would truly have been a very useful totem animal to have acquired, and unbelievably easy to boot. Why in blazes had she never bothered to snip a few hairs from some steed's name on her way north from Sangen? Well, no worries, if she found her way back to Karnor in the near future she wouldn't neglect such a simple and useful form again!
"Okay, Destyn, I think I'm done with this. Let me just tie the staff to your back-"
Imogen willed the length of wood to cease floating and finished tying it loosely to the boy, humming the melody of an old tune she'd heard in the Pfenning (which, had she thought about it further, she'd have dropped; it was rather macabre to hum a tune about drowning sailors before dragging someone into the ocean). It took her only a moment to finish the contraption and she stood back, beaming at it.
"And here is the bag, as promised, with the vents that no buggie can penetrate. Now, I will return to the albatross-shape. When you are ready, simply swim out into the water, and I will be right above you."