I am fighting lemur.

<xxxhp xxxm xxxmv>
A sifaka lemur bites you.
A sifaka lemur's bite injures you.
A sifaka lemur has a few scratches.

<xxxhp xxxm xxxmv 22700tnl 3 AM outdoor civilized fighting> c buoy
A turmoil unsettles your stomach as the sensation of having weight leaves you.
You feel light as a feather!
A sifaka lemur has a few scratches.

<xxxhp xxxm xxxmv>
A sifaka lemur's bite maims you!
...

The spell worked on myself, not lemur. The same thing happened another time with metabolic slowing(not completely sure about that).

Buoyancy isn't considered offensive if it is cast on yourself, so you are the default target.

valguarnera@carrionfields.com

If you are not fighting and cast buoyancy without argument it says "On whom?", so you have to use "c buoy self". Also, one has no way to cast it if he does not see the target(blind, etc). The same used to be with grease and adhesive web(they also required explicit target at first) and it was changed.

It does not work this way on mobs. If you fight a mob and cast it without argument, the mob will be affected, as expected.