Charles Ellicott Commentary Luke 8:23

"But as they sailed he fell asleep: and there came down a storm of wind on the lake; and they were filling [with water], and were in jeopardy." — Luke 8:23 (ASV)

He fell asleep.—The verb so rendered differs from the “was asleep” of the other Gospels, and this is the only place in the New Testament where it occurs. It is a somewhat more technical word and is, in that respect, characteristic of the physician-historian.

They were filled.—Better, they were filling, the tense describing the process, not the completion.