Slotwin, do not take water from a spectator, the risk of a DQ is too great. You can have a bottle of water in you shoe bag for when you finish the swim for the run to T1, but take it with you, do not litter. Better still, extra strong mints are good, just to freshen the mouth.
As to wetsuit, I'd completely remove it on the ramp and carry it, T1 is often like a war zone with people struggling to finish removing their wetsuits which have dried out and stuck to their legs.
If you've got any queries or concerns, just ask, I've finished IM Wales three times, and volunteered once, so seen it from both sides.