Buy lorry loads of soil to build to the required height, If your pond is extensive then the digger could probably just dig the soil required from the bottom or the edges of the pond this will obviously need to be done with a mechanical digger and you will need to drain the majority of the water from the pond to begin the work, then get some plants established asap to hold it all together.
As Ratter clearly explain, it would be a huge task in that depth of water!
An alternative might be to build a floating raft island and anchor it out there. I'm sure you can find plans for one of these with your search engine, I believe they are often refered to as an ' off shore laofing area'
All the Best Tbird+
Ps I think you need about 6"-8" of soilt to get plants established.