Sam is currently swimming or almost crawling on the sea bed with his water elemental transformation. He was extremely fast until he left the zone where he excreted all the poison, but after he left the zone, he merged with the sea bed and started moving slowly.
While he is moving, two Sea folks came near the poison zone in a hurry to look at the commotion. The beasts are not exactly powerful. All of them are initial stage Pre-transcendent stage beasts and even some Nascent stage beasts.
They are extremely weak. Their main aim is to halt the enemies that might have infiltrated in and keep them busy while sending the message to the Sea folk so that they can come and deal with the enemy.
And in many years, there was never a single elf or human that came into the water, so they became a bit lax. But still, they followed the orders to the point and came to check.