Learn Italian: Dovresti sperare che il corallo sopravviva nell'oceano. - You should hope that the coral survives in the ocean.

We use the subjunctive mood here because the main clause expresses a hope using sperare che (to hope that). Whenever we express a hope, wish, or doubt about a different subject doing an action (you hope, but the coral survives), the following verb must be in the subjunctive.

How is the subjunctive formed for a verb like sopravvivere?

Sopravvivere (to survive) is an -ere verb. For regular -ere and -ire verbs, the present subjunctive uses an -a ending for all singular subjects (io, tu, lui, lei). That is why the third-person form meaning it survives becomes sopravviva instead of its normal indicative form sopravvive.

Why is it dovresti sperare instead of devi sperare?

Dovresti is the conditional tense of dovere (to have to). Translating literally to you would have to, it is the standard way to say you should in Italian. It softens the sentence into advice rather than a strict obligation like devi (you must).

Can I just say in l'oceano instead of nell'oceano?