Liyinva suddenly tenses, and jams her oar into the water. Her voice, however, remains surprisingly calm as she announces "Attacker on the left" and nods at something just outside the boat. As the boat begins to turn to the right, Liyinva lets go of the oar with her left hand, grabs hold of the lead between finger and thumb, and drops into a combat ready pose, her fingers poised like the fangs of a snake as she glances around the area outside the boat, scanning for more enemies.
Spoiler: OOC
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Alerting everyone that we're about to be attacked, and spending my action making a more active perception check to see if there are more enemies like the one we saw. Also steering the boat.
Edit: A moment later, Liyinva calls out again in a rather more alarmed tone. "There's another one under the boat!"