Alkenes do not undergo hydration upon treatment with water even at very high temperatures.  There are two approaches to hydrating alkenes:
1. Reaction of the alkene with water in the presence of a strong-acid catalyst.
2. Using an indirect method

Hydroboration-oxidation, sometimes casually called hydroboration for convenience, is a common indirect method used to hydrate alkenes.

net reaction:

The  protocol is carried out in two stages:
Stage 1: Hydroboration
The alkene is treated with a source of borane ( diborane or borane-THF complex), which converts the alkene into a trialkylborane.

Stage 2: Oxidation
The trialkylborane is treated with H2O2 and a strong base, usually NaOH, in aqueous medium, which converts the trialkylborane into an alcohol.

Stage 1:

This reaction is an anti-Markovnikov addition and a syn addition.

Stage 2:

Stage 1 + Stage 2 =

The net reaction is an anti-Markovnikov addition:

see also oxymercuration-reduction

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