How deep must a lake be for fish or squid to spawn in it?

I have a small Lake in front of my house in Minecraft. It is currently 1 block deep.

My Question is, how deep (in blocks) must it be that I can fish in it and make squid spawn in it?

According to the Minecraft Wiki page on squid and fishing, squid will spawn at any depth water, any light level, and the fishing requirements are:

at minimum, the body of water should be 1 block by about 10 for casting distance. The water can be 1×1, but this requires the player to cast upwards so that the bobber will land in the water. This ensures the bobber's initial velocity is wasted moving up, so that it does not hit any blocks falling back down.