[Shiro's focus, when he first jumps into the water, is entirely on Keith-- trying to get to him. He knows immediately when Keith passes out (hopes it's just him passing out, not something worse, god, no--) and that's when his focus shifts to getting Keith the fuck away from the monster.]
[His movements are, obviously, limited while swimming-- but it doesn't matter. His entire focus shifts to getting Keith out, to protecting him, to making sure he's okay. The monster's not letting go of Keith, in any case, and rounding a bit towards Shiro, which makes it easier for him to reach the creature. His hand's glowing with familiar energy, and he's coaxing it into a blade, jabbing it up towards its jaw in the hopes of making it release Keith.]