Closest Place to Scan Multipurpose Room

Where is the easiest place to access a wreck with a multipurpose room for scanning?

The multipurpose room is not found in wrecks. You will stumble upon them naturally when you investigate the life pods mentioned in radio transmissions and then investigate the locations mentioned in the audio logs you find in them. But if you really want it now, spoilers ahead:

The closest to the starting location based on distance alone would be:

The one in the jelly mushroom cave. There are various cave entrances in the red grass biome which lead down there. The entrance which is easiest to find is the one right next to life pod #17 (the first one you get a message about). However, diving down there safely will require a Seamoth with the first pressure upgrade.

But the easiest and safest to reach would be:

On the floating island. Just swim about a km south-south-west from your starting location towards the conspicuous fog cloud. All the equipment you need is your scanner. You can also pick up some other useful things here, like the furniture you need to cultivate plants and the seeds for some very nutritious ones you can grow inside your habitat (bring a knife).