Bucket of water in boot

I have been reading various threads on leaks in the boot etc but thought it easier to jsut ask is someone can pinpoint where it might be coming from;
Went to charge VERY dead battery and lifted boot lining only to discover the left hand side of boot just by the light is saturated in about 2' of water. I unscrewed the plastic box by the light and dried it all out. This water was sitting on the internal wires for the left light.
My 5 has been sitting in this bad weather for about 6 weeks now and was wondering could the water be getting in round the light seals (I would think unlikely), from the hardtop fitting on boot or drainrails? Any advice much appreciated.
Meanwhile I am trying to re-charge my battery which even though jump started for 15 mins would only give sufficient charge for the lights to work. I took it out and have it charging in the house now for last 12 hours or so and it's still not re-charged...reckon I have to buy a new battery?? Really hope not.
Cheers
Went to charge VERY dead battery and lifted boot lining only to discover the left hand side of boot just by the light is saturated in about 2' of water. I unscrewed the plastic box by the light and dried it all out. This water was sitting on the internal wires for the left light.

My 5 has been sitting in this bad weather for about 6 weeks now and was wondering could the water be getting in round the light seals (I would think unlikely), from the hardtop fitting on boot or drainrails? Any advice much appreciated.
Meanwhile I am trying to re-charge my battery which even though jump started for 15 mins would only give sufficient charge for the lights to work. I took it out and have it charging in the house now for last 12 hours or so and it's still not re-charged...reckon I have to buy a new battery?? Really hope not.
Cheers