Probably nothing. Check that the battery is fully charged and the connections to the radio are sound. Receiving only takes a little power; transmitting takes a lot and a low battery or bad connection will fail on transmit. Check that your radio is set to the correct channel plan.
A damaged antenna is unlikely to work well enough to be of any use. For these situations, you should have an emergency VHF antenna on the boat. Our emergency VHF antenna, P6031, has a telescopic whip which extends to a full performance marine VHF halfwave antenna when in use. It comes in a plastic storage container 330mm long, so it can be easily stowed. It’s rated “best buy” in Sailing magazine's test of emergency VHF antennas.