Marty had noticed the crabs too, but wasn't too worried when they scuttled away.  "Actually, they seem more scared of us than we are of them."  Which didn't make that much literal sense when applied to a group, but that's how the saying went.

"It might be good XP to take them on."  She added.  "And they might even have loot from prior shoppers in their nests."  She didn't sound overly enthusiastic about carrying through with the idea.

If they do not wish for a fight let them lie.

Jennifer, hearing the scuttling, couldn't help but let her curiosity overtake her. While the others were talking, she decided to inch her way over to the passage and peek her head in to see what was going on.

Marty wasn't much interested in fighting crabs.  But the louder than average splashing and scuttling caught her attention and she turned to investigate.

Only to find Jennifer ahead of her inching towards the cave mouth.  She hadn't realized before, but Jen was kinda hot.  With her firm round behind and cute little tail and girlish silhouette.  She was shocked that the sight didn't do anything for her.  Things were getting worse.

She focused past the sight of pretty tiefling and toward the cave opening, doing her own version of sneaking stealthily toward the source of the disturbance.  Her dark clothing blended really well with the shadows, but she wondered if Leo was watching her from behind?  Or was he watching Jennifer instead?

Jennifer squeaked as she realized she had attracted the crab's attention. Without thinking she stammered out a prayer. "Dear lord Asmodeus, sorry to bother you but there's a giant crab attacking me, please help! Thank you, Nos nihil ante vos!" as she finished a gout of crimson fire suddenly burst from below the crab to engulf it in flames.

(Casting Sacred Flame cantrip, Dex save required from the crab dc 13)

she then called back to the rest of the party. "Guys! I'm really sorry but I think I made the crab mad! Please don't be mad at me!"