Help needed, what to do when line is completely snagged

I just wanted some advice, im into my second year carp fishing and one or twice ive caught a fish only for it to run to the margins and the line becomes totally stuck.

I have no idea if the hook has been transferred onto a bit of wood, if perhaps the line is snagged around something with the fish still hooked, but either way its totally stuck and dispite reeling in as much as I can with the line very taunt it doesn't budge.

Ive tried leaving the fish for a while. Tried keeping the tension on for a while - most of the time nothing works.

I obviously need to try and steer the fish from the margins earlier and more effectively, but any suggestions of what to do in thos type of situation.

Thanks