Schengen visa requirements for seafarers signing off

I assume there is some reason why you couldn't apply for a proper visa (that is still valid) in advance, like eg.

• your visa was supposed to be valid when arriving in Spain, but the ship had some unforeseen delays
• you didn't plan to leave the ship in the Schengen are at all (but some reason happened, like sick relatives, job terminated, or whatever)
• you didn't even know where you will be at the date when you're supposed leave (no idea what ship you're on, but for some types I guess that's possible)

or something like that, and that you have some sort of evidence of that (even if it's "ask the captain", just something).

Without any reason why you didn't just apply in an embassy/consulate in India, it's going to be hard.

Furthermore, I assume

• that you have your passport, it's valid, not damaged and so on
• your passport does not expire in the next 6 months
• your expired visa still exists and you can show it to the border guard (big help)
• you have evidence that you work on the ship
• in Spain, you just want to go to an airport to fly to India, nothing more (especially no visit to another Schengen country).

In this case, you can be pretty sure to get get a very-short-term visa (max. 5 days, possibly shorter) directly from the authorities in the harbor in Spain.

Sources:
The Schengen border guard handbook section 3 and 7

You ought to be able to get a visa at the port were you disembark, under Article 36 of the Schengen Visa Code. However, this is subject to the requirements set out in Annex IX, and it requires cooperation of your employer:

Article 36

Visas issued to seafarers in transit at the external border

1.  A seafarer who is required to be in possession of a visa when crossing the external borders of the Member States may be issued with a visa for the purpose of transit at the border where:

(a) he fulfils the conditions set out in Article 35(1); and

(b) he is crossing the border in question in order to embark on, re-embark on or disembark from a ship on which he will work or has worked as a seafarer.

2.  Before issuing a visa at the border to a seafarer in transit, the competent national authorities shall comply with the rules set out in Annex IX, Part 1, and make sure that the necessary information concerning the seafarer in question has been exchanged by means of a duly completed form for seafarers in transit, as set out in Annex IX, Part 2.

3.  This Article shall apply without prejudice to Article 35(3), (4) and (5).

The most relevant part of Annex IX:

II.   Leaving service from a vessel that has entered a Member State port (exit from the territory of the Member States)

— the shipping company or its agent shall inform the competent authorities at that Member State port of entry of seafarers subject to visa requirements who are due to leave their service and exit from the Member States territory via a Member State airport, land or sea border. The shipping company or its agent shall sign a guarantee in respect of those seafarers that all expenses for the stay and, if necessary, for the repatriation costs of the seafarers will be covered by the shipping company,

— the competent authorities shall verify as soon as possible whether the information provided by the shipping company or its agent is correct and shall examine whether the other conditions for entry into the territory of the Member States have been satisfied. The travel route within the territory of the Member States shall also be verified e.g. by reference to the (airline) tickets,

— where the verification of the available data is positive, the competent authorities may issue a visa the authorised stay of which shall correspond to what is necessary for the purpose of the transit.