Talking Dante Episode 19 – Should (but not ought to) can be used in Type 1 conditional sentences to make the condition less probable (per rendere la condizione meno probabile). ‘If you see Mary …’means that I think you will probably see her (se vedi Mary …). In cases where I think that is less likely (meno probabile), I can use ‘If you should see Mary (se dovessi vedere Mary …). Should can also replace (rimpiazzare) if – Should you see Mary … In the place of should you can also use happen to – If you happen to see Mary … (se per caso veda Mary; se capita che vedi Mary). Happen to cannot replace if, but you can also use should with happen to – If you should happen to see Mary … / Should you happen to see Mary (se dovesse capitare che tu per caso vedessi Mary …)
Break free (liberarsi) is one of a number of expressions formed with the verb break. Basically, this expressions means escape from an (unpleasant – spiacevole) person or situation that is controlling your life. Break free is stronger and more vehement (energico) than get free.
Clutching (stringente; che stringe) is an adjective that comes from the verb clutch or grasp tightly (stringere forte, tenere stretto, aggrapparsi). The idea is that the sea does not want to let you escape!
If you are fighting for breath then it means you are having great difficulty breathing (lottare per ogni respiro).
Flat is an adjective that has many different meanings. If you are lying flat-out (giacere ventre a terra), it means that you are lying full-length (per lungo, tutto disteso), in this case on the sand.
Gape (guardare a bocca spalancata) is a verb that in this case means look at something with wonder (stupore) or incredulity. Basically, gape means open wide (spalancare) and you can use it to speak about your eyes (as here) or your mouth (with the same effect of wonder and incredulity).
Waves or the surf (la parte schiumosa delle onde) can pound (battere forte, martellare) on the beach. Here the adjective pounding means beating, thumping (che colpiscono) or pummelling (che percuotono) on the sand.
In that kind of situation your face would be white because you are scared or because you have been too long in the water. Swollen (gonfio) is an adjective that means abnormally tumid or enlarged (rigonfio) or protrubent after injury, etc, or because, as in this case, you have spent too long in the water. Your face is swollen probably because it is waterlogged (impregnato d’acqua).