John Chrysostom

And observe how unassuming the expression is. That he may not seem to prophesy, but to speak as of conjecture, "I perceive," says he. For they would not have received it, had he said this at the outset. In fact he does prophesy on this former occasion, as he does afterward, and says there, "The God whom I serve," leading them on. Then how comes it that it was not "with loss" of any "of their lives?" It would have been so, but that God brought them safe through it. …

Homily on Acts 53 ↗

Theophylact of Ohrid

But to show that he is not prophesying, but speaking by conjecture, he expresses himself thus: "I perceive," – because they would not have immediately believed him even if he had said this as a prophet.

Commentary on Acts ↗

Oecumenius

Even if the shipwreck did not occur to them with loss of lives according to his word. For this would have happened as far as the nature of the thing was concerned, if God had not preserved them. For through him he also caused those men to be saved. The shipwreck that took place, then, occurred because the season was bad, since the storm was great. The marvel is greater, that in such a season they were saved from the dangers, both the Apostle himself and through him the rest. Therefore he was not proved false.

Commentary on Acts ↗