How can I remove sealant from shower?

Moved into a student house. One of the showers is a bit grubby - the sealer all around the bottom of the shower is black and disgusting. It needs removing and replacing but I'm not sure how - it's not like the white sealer I've been using in the bathroom, it's more a clear plasticy type. It won't seem to budge just using a knife as it's very springy and plasticy.

Any ideas?

Elise
September 2006