Thinking about it, I'm in the snakes don't crawl camp.
Remember meanings of words shift over the years, so any past results don't necessarily apply present; you need a continuous line of examples. [Counterexample: "Stink" used to mean "(give off) smell" but is now since long strictly for bad smells; similarly "smell" is not neutral by now ("something smells here" is negative, you're not thinking "ah, like lemon house cleaner, or mown grass, or something a priori neutral)]. Specifically poetic usage cannot be used as an argument; so you need a line of normal, non-poetic prose usage examples. And "crawling seas" rather clearly suggests an amorphous mass undirected by a head having grasping hands, so it's a bad/counter argument.
For present usage, I'd hazard (unsourced) that when using the verb "crawl" we get hands/legs in mind, from any "creepy crawlies" (=any relatively small non-fluffy animal that gives you goosebumps; person-dependent; might contain snakes as it's an undefined term that appears in e.g. kids' animal programs and they'll fit in anything they have on hand), to "front crawl" in swimming (which is a "belly crawl" if you imagine the water being mud, like on an assault course, and your legs became disabled; sorry, time of the year, still thinking of Flanders' Fields).
Most sensible is in general to look at etymology but that seems unclear. If it's related to the cited words, then fingered hands/feet are very much implied. [Dutch kruipen seems cognate to creep to me, and it's what rug rats do before toddling; dutch krabbelen is what pets scratching at doors to be let through do, etc.] That's what makes it a good question.
Also, note several-times cited dictionary definition "crawl verb. 1b: to move with the body close to or on the ground." does not clearly apply to snakes: The propelling force is in hands/feet! (A sidewinder snake propels itself "close to the ground" but it's definitely not crawling.) This definition is writing from the "normal" viewpoint of a body being well off the ground, so "crawling" is "with the body close or even on the ground".