Perhaps it would have been a better idea to flee as soon as you were able to, and not stick around right by the edge of the water teasing the sludgy creatures inside. The water writhes and churns from their thrashing, and perhaps you shouldn’t be so startled when one of the fish is flung at you, knocking you over.
You aren’t given the chance to struggle, your vision swimming from the fall as you try to reorientate yourself. Not that the goo lets you- even if you can’t see it you can feel it melting across your body in a writhing mass of warm wetness.
You can feel your legs disappear, feel the fins replacing your ears as you lay there, gasping for air as the slime overtakes you, outside and in. It’s over just as quickly as it began, your human form gone in the waves as spikes tear away the remnants of skin to reveal the new scales beneath...