Why ransom offered little safety at sea

Were the chances of being ransomed much lower at sea during the Hundred Years' War?

Yes; captured crews were commonly thrown overboard, so wealth and heraldry offered far less protection than on land.

Rich heraldry could advertise a valuable prisoner on land, where captors had space to hold and exchange people. A captured ship at sea presented immediate security and manpower problems, so crews faced much harsher treatment. Throwing defeated crews overboard was described as standard practice in this setting. Combatants therefore had stronger reasons to fight to the end because surrender offered little expectation of safety.