I suspect I'm being mildly unreasonable but not completely.
In a nutshell: on holiday in Spain with extended family. I am from Australia and grew up around swimming pools and with high awareness of water safety. Rest of family are good swimmers but from cold climate.
Family here have 3 DCs, 7, 5 & 3. We have a 4yo and a 2yo. Neither can swim at all and I watch them like a hawk around the swimming pool, which has a fence with a gate. The 7yo can open the gate and constantly leaves it unlocked.
The 5yo had a near-drowning incident on holiday 2 years ago. I have therefore been fairly shocked that the parents seem fairly relaxed about watching him (and the others) in the water. Last night I heard that there have been 2 further close calls this past year 
Long story short: DH and I were meant to leave our 2 DCs in care of family and go out for a few hours. I had a literally last-minute wibble and refused to get in the car. Said I would not enjoy myself as I would not be able to relax. Am now sitting watching my DCs (they are not in the pool while I'm MNetting!) and feeling slightly sheepish as well as v annoyed and emotional. DH and the others have gone without me. WIBU?