On the one hand, this is a terrible idea. On the other... well, you might have juuuust the skill to help out here.
You swim to the pipe, positioning yourself above where the crystal is lodged. They, aiming your cannon, you fire a [Force Wave]. While the attack hopefully won't deal damage to the structural integrity of the pipe due to its weak nature, the heavy knockback it has should hopefully knock the crystal loose.
>Frisk: Begin ill-advised gambit "Attack the pipe."
You swim to the pipe, positioning yourself above where the crystal is lodged. They, aiming your cannon, you fire a [Force Wave]. While the attack hopefully won't deal damage to the structural integrity of the pipe due to its weak nature, the heavy knockback it has should hopefully knock the crystal loose.