Whenever i boat dive, i have at least a basic plan for what to do if the boat isn't where it should be! Make that plan!
A simple look at a map (or these days google earth etc) will give you an overlying idea of the terrain (merrain ??) and will let you quickly estimate distances and likely current flows based on local topology. That straight away might suggest "no point trying to swim to shore" or it might suggest "if we aim for that easily identifyable rocky outcrop we can see an easy to approach small cove at the bootom with an access path providing a safe egress point" etc
Carry an dSMB. The only time i don't is when in a pool or aquarium
Yes a nice bright, long one is better, but any dSMB is better than none, and it can also be used for redundant buoyancy, u/w and at the surface.
Talk to your dive buddies and group BEFORE you jump in to decide at the very least a basic plan upon surfacing. Who makes up your Team for that particular dive is going to have a huge impact on your plan. You might be diving with a team of ex navy seals, who can swim three and a half miles u/w on a single breath, wrestle through 7 foot of heavy surf in their full kit and run up the beach without so much as getting out of breath. You also might be diving with someone in their 70's, or with children, for whom any kind of excessive physical or mental stress is to be best avoided (although to be fair, some of the older divers i know are the fittest people i've ever met, and would almost certainly already be in the bar with a cold drink by the time i fish myself out of the sea
So, make a plan, and talk about that plan. Certainly doesn't have to be rocket science, but it might just save your life (or at the least turn a stressful, worrying situation into a slightly less stressful, worrying one)