First off, D.D. Degg at The Daily Cartoonist caught a great subject-matter duplication in both the 9/13/26 Mark Trail Sunday strip and the 9/14/26 Ripley’s Believe it or Not panel. Both strips feature raccoons, but specifically, Jimothy, the short-spine celebrity raccoon. You can view Degg’s article here. Scroll down the page to see the topic. Interestingly, Ripley’s is published by a different syndicate. However, the real coincidence is the closeness of their publication dates, in spite of the fact that Rivera’s Sunday panel was likely drawn a few months earlier. Okay, moving on to today’s Mark Trail:

At last. At long last, we have some drama and danger. I’ve been hoping to see something in this otherwise superficial skit! And I’ll admit that—taking Jules Rivera’s drawing style into consideration—panel 1 presents a real sense of danger as these two figures disappear into the darkness below. And it is a plausible event, given the already-demonstrated instability of the cave floor.
Now, moving on to the other two panels, the situation gets murkier, and lighter. First of all, the dramatic darkness Rivera exposed Mark and Cricket Bro to was dispensed with in the other two panels. Perhaps Rivera didn’t realize what she had going in panel 1 and just returned to the “eternal daylight” she prefers. Or she didn’t care. But this daylight lessens the dramatic continuity. I think we all had similar reactions to James Allen’s cave adventures. Anyway, it’s a shame, since darkness has been one of humanity’s longest and most frightening environments, especially in strange places. In any event, the drama and danger of darkness is replaced by another dramatic element: the “surging underground river.”
Okay, so sure, an underground river is believable. Falling into a river, in general, presents the well-known danger of being swept away and drowning. But Rivera could have had both darkness and the river. In a related point, why did the surging flood waters from above stop (panel 2)? Did all of the cave water pour into the underground river at once? Or was it just a design decision by Rivera? It looks like she still has cave waters flooding around the opening, instead of falling into the hole (panel 2). Call me picky, but I don’t think that’s how flowing water works in reality.
An underground river can certainly be a problem, depending on the current and depth of the river. My patented, superficial research methodology shows that underground rivers tend to be between 3 and 10 feet. So, they can be a real danger to life, especially if you cannot swim or if you are encumbered by heavy clothing and equipment (or you are also in a dark environment!).
When Rivera first took over this strip in late 2020, she commented about her love of the classic three panel joke-a-day format and how she wanted to use that whenever possible. Well, she’s certainly made good on that aspiration over the years, and today is no exception. Marks fulfills the 3-panel punchline format by delivering his sarcastic retort to a scared-witless Cricket Bro.