It fills up too quickly.

The black liquid fills from the sides emboldened by your ejaculation. Two of the hands sprout further from the wall slowly forming a latex womam. You realise you have to escape before she forms otherwise you might never escape this well.

Your joints aren't moving as well because you've been in the black liquid too long. As you swim up your cock gets hard again this time at least 2 inches bigger. Both of these things coupled together make you shudder and look back at the latex woman only to realize she's already swimming towards you!