1. Crew should know the approximate diving time.
The recent tragic event in Kuching shown the search by the boat was at least an hr late after the supposed 30 mins dive. And they were so far out at sea that took them further couple of hrs to contact the authority and it was dark already.
2. Shoot the smb at safety stop. I do that most of the time.
One person I know even carried survival kit(high energy bar + water) in every dive(remote location only)
All of that sounds great. I wonder how much difference a pint or even a quart of water would make, but it'd be better than not having it.
Nothing beats an international network of satellites connected to Search & Rescue tho. If you're out of sight of land and drifting, it's a huge ocean. New Zealand with its rough terrain and long shoreline even has its own PLB Charity working with the local S&R resources.
https://www.locatorbeacons.co.nz/
They sell PLBs programmed for New Zealand citizens. The new ACR 425 View with its fancy LED screen is $589NZD = $430USD. That's a lot more money than most divers want to spend, but it lasts for 5 years on standby = $1.65/week and take it anywhere on the surface - land and sea. If you have to use it the manufacture will replace it with a free one in exchange for a good story; they have a wall of trophy PLBs from successful rescues. My older model is over 5 years old, but I got the battery replaced and the unit refurbished for about $100 - good for another 5 years! I take it everywhere tho, hiking, farming, diving, or just driving. It goes well in my carry-on for flights so I'll have it when I arrive.
Oh, for diving you'd need a dive canister. I got the smaller one for $110, replace the o-ring annually, grease the o-ring often - but the larger one is the same price I think to carry your power bar, water bottle, foil blanket, etc.
HDVSeatek Scuba Diver PLB Small Canister – WEAR IT AUSTRALIA!
The RescueME PLB is smaller and cheaper, and there are many older models like mine for sale. You'd need to have the battery replaced and the unit programmed for your country, but that's all doable. 90% of PLB alarms are false alarms so don't be one of those. Register your unit, learn how it works, and protect the activation button. They may not take an alarm seriously at first, but after some phone calls, they will go for you within the 24 hour strobe life. Or if your dive Op reports you missing, then they should match your name and go for you immediately.