The matter of bringing an appropriate amount of cables and chargers is, perhaps surprisingly enough, very important. It is worth considering purchasing a good charger with multiple usb ports — in case of ever having to charge multiple devices (for instance, photographic equipment, diving computer and flashlight) at once.
Every cabin has power sockets but if our roommate also has high energy requirements, we might find out there are not enough of those.
It is worth checking what plug types, voltage and frequency are used at our destination (Egyptian power sockets are compatible with European plugs; on the other hand Mexico is using the same standard as the USA).
When taking a dive light with a rechargeable battery, you need to respect the limitations imposed by air carriers. Rechargeable batteries (under 100 Wh, e.g. Teclight) are only allowed in hand luggage. Larger batteries require prior approval from the airline. Empty flashlights powered by regular batteries (Tecline US-16) are best transported in the checked luggage, while the alkaline cells themselves I would put in a carry-on bag. I have bad memories with batteries bought on-site. For most trips, I pack a spare flashlight and an extra dive computer for two people.