After all, none was needed.
"And I have three wounds from stones, and this man behind me as many more, beside a shot through his shoulder.

Now, sir, be we cowards ?" "You have done your duty," said Amyas, and sank down in the boat, and cried as if his heart would break; and then sprang up, and, wounded as he was, took the oar from Evans's hands.

With weary work they made the ship, but so exhausted that another boat had to be lowered to get them alongside.
The alarm being now given, it was hardly safe to remain where they were; and after a stormy and sad argument, it was agreed to weigh anchor and stand off and on till morning; for Amyas refused to leave the spot till he was compelled, though he had no hope (how could he have ?) that Frank might still be alive.

And perhaps it was well for them, as will appear in the next chapter, that morning did not find them at anchor close to the town.
However that may be, so ended that fatal venture of mistaken chivalry..