。
The net got tangled in the propeller.
Literal
Net [subject-が] propeller [in-に] became-entangled.
絡まる ('to become entangled, to get caught up') is an intransitive verb; its transitive partner is 絡める ('to wind around, to entangle'). に marks what it got entangled in — the propeller. Straightforward event description in plain past.