If you are travelling from Mumbai you have the option of travelling in a boat. There is frequent ferry service from the Gate way of India who would drop you to the Alibaug bus depot. Kashid is just 35 Kms from the Alibaug bus depot. There are A/c and non A/c ferry boats and travelling by ferry would be the fastest way to reach Kashid from Mumbai.
Alibaug town is about 100 kilometres from Mumbai, a two hour drive from mumbai. Once you reach the Alibaug circle take the Alibaug - Revdanda road. Once you cross the Revdanda bridge a 15 Kms drive will get you to Kashid