Crack in Shower - Sealant?

[cuteboxerdog]

Hi there - wonder if you can help! I have a walk in shower with a plastic tray - the tray has developed a hairline crack - not enough to let any water through at the moment!

My question is: Is there a sealant/membrane which is waterproof that I can apply to the crack to strengthen it so that it doesn't get any worse? If so where can I get it?

Your help is appreciated. Thank you.