According to HA HA Budys Here :
Code doesn't like electrical outlets or switches within 4' (or so,
details vary from code-to-code) from a shower or bath.

(1) Shower or Bathtub Space. Receptacle outlets shall not be installed in or
within reach [30 in. (762 mm)] of a shower or bathtub space.

Is that all US codes? Our code used to say "within reach", and then
it's been specified more exactly. And moved around a bit. This is
why I hedged.

It must be on a GFCI regardless (tho a permanently installed heater
may be code exempt if you want to be picky).

May be exempt, and is if it's permanently installed. I searched the NEC and
can't find anything that even remotely suggests you can't install a permanently
- connected, permanently installed in-wall heater or electric baseboard heater
right up against the bathtub...

H'm. You'd probably find them covered under the switch rules if it has any
user-accessible controls on them.

An ordinary portable heater would _likely_ be considered to be non-exempt from
the GFCI rules. The exemption is primarily for large appliances that wouldn't
move, like a dryer or clothes washer, which usually have excellent grounding
anyway. Or builtins of course.

To be exempt by latest codes, a plug-connected heater also have to be on a
single outlet receptacle.

Thus, a plug heater physically attached to something in the bathroom on a
single outlet may be exempt.

Ie: a B&D plugin cube fan heater would need GFCI. A wall/ceiling mounted
plugin IR unit probably wouldn't if it was on a single outlet.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.