I feel this lump in floor of mouth under tongue. any ideas?

Lump in mouth: See a dentist or an ENT specialist as soon as possible. Any lump in your mouth is not normal and needs to be evaluated.

Ranula or mucocle: Are the most common cause. The difference is mainly size, the ranula being larger (looks like the belly of a frog? Hence the name). What they are are blocked salivary gland ducts. The lump is the build up of fluid. They can be a one time event or continually reoccur. They can even reoccur after surgical removeal.