I like the idea of the mermaid being able to escape if she currently has a power-up that is still going while she’s in the shark’s belly.
Struggling with cajun would add red pulses to the shark’s belly, struggling with eel would just teleport you out and would require the least effort and there’d of course be the electric effect around the shark’s stomach, squid depend on if you have at least one clone available and the escape would only work if the size of two mermaids exceeded the shark’s max belly size, and with the pufferfish you’d see spikes poking the sharks’s belly during the struggle.
Even if actually escaping shouldn’t be a thing, the added layer of the power-ups adding to the struggle would be really cool to see.