Very direct storytelling, very quick pacing, very excessive use of music cues, very bad dialogue, very weak character writing, very bad scene writing - and, taking cues from kindred fare of the 1950s, an initial "encounter" which is mentioned in dialogue but which we don't actually see. All this and more, within only the first ten minutes. Yes, that's very quick to start making judgments, and I've seen some titles make a definite turnaround, but it's a poor first impression to say the least, on top of how the premise (and promotional artwork) rather recall a more famous series of creature features. As viewers we accept (to varying degrees) that some flicks are going to gleefully embrace the less earnest side of a genre, with no loftier goal than to be a fun little romp. How much fun such flicks actually provide is another matter. I don't think 'They crawl beneath' is completely rotten, but the viewing experience is saddled with compounding issues that place significant limits on what we can get out of it.
Those traits mentioned above that form our earliest impression remain factors in varying proportions. To these add the sudden emergence of a new species of worm, earthquakes that strike exactly when the story require them, and the circumstances in which protagonist Danny becomes trapped as suggested in the premise. It's a lot that the picture throws at us, and a lot that it asks of us under the unspoken agreement of suspension of disbelief. The difficulty is that between these major story elements and the swift pacing, let alone the other weaknesses, that disbelief is hard to surrender, and the possibility is quite dampened of there being any thrills from the conglomeration. As the length draws on, it further becomes evident that basic entertainment hangs by a thread, and it's the baseline level of entertainment that follows from most any conglomeration of light and sound. Moreover, the direction isn't necessarily the greatest; the cast do what they can under the circumstances, though I think they make a decent enough go of it. The practical effects are actually mostly pretty terrific, though may be employed to more questionable ends; the post-production visuals are a little too obvious, though better than a lot of other examples. 'They crawl beneath' also comes across at points as overproduced, accentuated by, of all things, how wholly impeccable Karlee Eldridge's makeup seems to be any time we see her.
Would that screenwriter Tricia Aurand didn't also try to weave in bits about the protagonist's personal life, which are irrelevant to the scenario and direly weigh down the proceedings. The root narrative is fine, if simple, but the specifics that flesh out these eighty-seven minutes are much less sure-footed, including dialogue in the last third or so that seems to senselessly and arbitrarily contradict earlier dialogue. Oliver Goodwill's music ranges from suitable to good, if unremarkable, but is plainly overused here and far too prominent. What it all comes down to is that this is a movie with distinct flaws and shortcomings, and which is troubled still more by too little strength, and too little vitality; there are no meaningful dynamics or meaningful progression, and in turn no meaningful tension or suspense. The course of events is just presented rather flatly, with each beat and inclusion tossed in in the most straightforward, unsubtle manner possible; it's surely longer than it needs to be, and the last stretch following the climax may be the lowest point of all. It's not abjectly terrible, yet for all the hard work that went into it, this is effectively a horror flick by the numbers, with no heart to make any of it count. Add in all the other discrete problems, and watching becomes a tad laborious. If you happen to come across it then there still far worse ways to spend one's time, but regrettably, there's just not any real reason to spend time with this in the first place.
