ibiza in october...

[CEREBRAL]

Will it be warm enough to swim in the sea?

[Dassie]

This depends on your interpretation of warm. Yes to me it's warm enough - you can probably equate it to the Atlantic at Tenerife

[Sootz]

Was there last year in October and swam in the sea no problem.

[netibiza]

Yes, October is usually a warmish month over here. We are having a bit of a stormy time at present so you could be lucky. Water will be "fresh" but quite swimmable.

[ianess]

October is at the tail end of the tourist season but we were there from the 15th to 25th a few years ago and it was lovely. Sea temperature at Es Cana was ideal for swimming.
Explore the island.....it's beautiful and didn't deserve the reputation that it got because of media coverage of a few idiots.
Have a great time.