General:
* Indulge
* Revel
* Bathe
* Immerse
* Submerge
* Savor
* Roll
* Lounge
* Lie
* Dwell
Negative Connotations:
* Drown
* Stew
* Smother
* Languish
* Grovel
* Mope
* Slump
* Plunge
Specific to Animals:
* Roll around
* Mud-bathe
* Sunbathe
* Lie down
* Rest
The best synonym for "wallow" will depend on the specific meaning and tone of the sentence.