Question: You often *plunge* into the sea or *plunge* you hands into your pockets.

Can the word be used to describe a "horizontal immersion"?

Example sentence:

> 
> She opened the door and **plunged** into the blinding sun.
> 
> 
> 

If not, what's a more appropriate word?

Answer: 
The OED's first meaning of ***plunge*** involves transitively thrusting, throwing or dropping something (or oneself) into a liquid - from the French ***plonger*** - *to jump into water, to submerge, or sink*

However, sense 4 (intransitive) of the verb covers precisely the circumstance you relate:

> 
> 4. intr. To move or travel forth, on, etc., rapidly, abruptly, or recklessly; to move with a rush or sudden impulse into or out of; to
>  hurtle, career. Also fig. 1726 W. Broome in Pope et al. tr. Homer
>  Odyssey V. xxiii. 256 He views the strand, And plunging forth with
>  transport grasps the land.
> 
> 
> 1806 T. Jefferson Let. 5 July in Writings (1984) 1165 If the
>  executive is to keep all other information to himself, and the House
>  to plunge on in the dark, it becomes a government of chance and not of
>  design.
> 
> 
> 1834 L. Ritchie Wanderings by Seine 110 We..plunged into the high
>  road leading to Duclair.
> 
> 
> 1885 Manch. Examiner 22 Jan. 5/2 Under a well-organised fire from
>  the works, the Arabs plunged forth upon the square.
> 
> 
> 1891 C. Graves Field of Tares iv. vi. 241 The Norwich Express,
>  plunging out of Liverpool Street Station.
> 
> 
> a1902 F. Norris Pit (1903) x. 400 She had committed herself now;
>  recklessly she plunged on.
> 
> 
> 1954 Times Lit. Suppl. 12 Nov. 714/4 As the Age of Reason plunged
>  towards revolution, Juvenal was carried like a banner in the van of
>  the attack.
> 
> 
> 1990 A. Stevens On Jung ii. 18 The dreamer might see a train,
>  carrying him home, plunging in and out of a series of tunnels.
> 
> 
> 2004 Derby Evening Tel. (Nexis) 16 Mar. 6 If the Germans had
>  captured crossings over the Trent, they could have plunged in any
>  direction.
> 
> 
>
Almost all definitions of Plunging seem to imply that it's a word describing vertical descent.
[Merriam Webster](https://www.merriam-webster.com/thesaurus/plunge) thesaurus includes the following words as related:

> 
> dip, immersion, submersion; fall, plump, slip, spill, stumble, tumble; descent, drop; belly flop, header, jackknife, swan dive
> 
> 
> 

None of them indicating a horizontal direction.

Also, [Thesaurus](http://www.thesaurus.com/browse/plunging) synonyms imply a vertical nature.

It may be acceptable to use *plunging* in the sentence but you may not get the intended effect on a reader.
Maybe the following will suit better

> 
> She opened the door and **stepped** into the blinding sun.
> 
> 
> 

or

> 
> She opened the door and **charged** into the blinding sun.
> 
> 
>