A unique mutant found on the west coast, the Floater is an engineered mutant, a Flatworm infected with Forced Evolutionary Virus.

Originally they were meant to appear in New Vegas, but according to Josh Sawyer, the project director:

I think Floaters are cool critters in the Fallout universe, but, like Centaurs, they have really weird bodies that require unique animation rigs. From an animation perspective, limbless flying things tend to be really cheap (usually), human-like bipeds are cheap, quadrupeds aren’t too bad. Once you start getting into creatures with multiple heads, snake bodies, tentacles, etc., they get really expensive. IIRC, we talked about having Floaters but we just didn’t have the animation time for them." Source

Simply put, this mod restores Floaters into the game, including their Budding and Evolved subtypes.

Stats:
Floaters can be summed as "The opposite of centaurs, smaller hitbox, quicker, melee only" Floaters are quick and have a lot of health and damage (much like in Fallout 1/2 where they were pains in the arse to deal with)

In terms of sound design, they use the Centaur's SFX, which while not perfect is a solid fit for them.

Floater
Level: 12
Health: 450
Attack Range: 48
Attack Damage: 50
SPECIAL:  5 10 10 1 1 10 5
Turn Speed: 250
Speed Mult: 300%
Fatigue: 500

Budding Floater
Level: 16
Health: 550
Attack Range: 48
Attack Damage: 75
SPECIAL:  5 10 10 1 1 10 5
Turn Speed: 250
Speed Mult: 300%
Fatigue: 500
Scale: 1.25

Evolved Floater
Level: 27
Health: 750
Attack Range: 128
Attack Damage: 100
SPECIAL:  5 10 10 1 1 10 6
Turn Speed: 250
Speed Mult: 300%
Fatigue: 500
Scale: 1.25

This mod also adds a new form of Food called Floater Bulbs
-35 Starvation (hardcore)
3 HP over 15 seconds (default, 0 Survival)
+12 Rads
Worth 15 caps

Floaters drops include:
Floater Bulb: 25%
Floater Bulb: 75%
Centaur Blood: 25%

Locations
Typically found wherever Centaurs can be found, such as: Jack Rabbit Springs, Black Mountain Crater, Crescent Canyon and Devil's Throat.

In total there are 31 Floaters, and they respawn.