Learn Finnish: Menimme tutkimaan haaksirikkoa, koska siellä lienee ollut salainen symboli. - We went to study the shipwreck because there probably was a secret symbol.

The potential perfect describes an action or state that probably happened in the past. It is formed using the potential mood of the auxiliary verb olla (here, the 3rd person singular lienee) plus the past participle of the main verb (here, ollut). Together, lienee ollut translates to 'probably was' or 'might have been'.

Why do we use the form tutkimaan instead of the basic dictionary form tutkia?

The verb mennä (to go) is a verb of motion. In Finnish, when you go somewhere to perform an action, that action verb must be in the illative form of the third infinitive. This means adding a -maan or -mään ending to the verb stem. Therefore, 'we went to study' becomes menimme tutkimaan.

Why is haaksirikkoa (shipwreck) in the partitive case here?

The verb tutkia (to study, to investigate) is a partitive verb. It takes a partitive object because the action of investigating is typically viewed as an ongoing, continuous process rather than an action with a definitive, completed result.

Why is the subject salainen symboli in the nominative case when it comes at the end of a 'siellä on' (there is) type of clause?