Suspenso is a fascinating word because it has a double meaning that plays perfectly into the song's theme. It can mean 'suspense' or 'suspenseful', referring to a state of anxious anticipation.
However, in a school context, suspenso also means a 'failing grade' or 'fail'. The singer uses this word repeatedly, saying "llevo ya más de un suspenso" (I already have more than one failing grade), implying he's failing at something, likely in love or in expressing his feelings. This clever wordplay makes it memorable and adds depth to the lyrics.
Have you ever been so nervous to meet someone that you feel like you're literally floating off the ground? That's exactly what Dani Fernández sings about in "Supersubmarina"! He describes arriving at a place, trying to look calm, but inside he's "temblando" [trembling]. He feels like he'll have "el cielo entre mis manos" [heaven in my hands] if things go well, but he's also afraid of getting a "suspenso" [failing grade] in this