Is it possible that someone might find it?

Of course it's possible. Who knows how likely it is, though.

If it was flushed or otherwise went down the drain of a domestic water system, it will end up at the water treatment plant eventually. It will likely be caught in a filter there and will, most likely, never be seen again because it will be scraped out with all the other trash and sent to the landfill. It's possible that someone will see it and decide to grab it.

If it fell into a natural body of water, there's no telling where the currents might take it. If somebody were to ever find it, they might let it dry out and try to read it to figure out who it belongs to in order to return it. i.e. be a Good Samaritan and try to get your valuable pics back to you. They might also just pick it up and toss it in the trash.

Is it possible ... to get the data

It depends on what you mean by "it snapped in two halves":

1. It was a "horizontal" snap - the plastic case came apart, separating the top from the bottom half of the case. In the situation, the circuit board and chips are still all in one piece.
   1. If the case came off, someone could, after letting it thoroughly dry, probably just put it in a reader and have a high chance of getting data back.
   2. They might be able to put the halves of the case together, then hold the whole thing together as they slide it into the reader.
   3. If they cannot get the pieces to fit back together properly, they might be able to push it into the reader, then gently wedge something in on top to hold the contacts on the card against the contacts in the reader.
2. It was a "vertical" snap - the circuit board itself is broken
   1. They (or someone skilled at soldering under a magnifier) might be able to solder all the traces together with jumper wires and then be able to read the chip in a standard reader.
   2. This might take professional assistance, which would cost them. They'd have to decide if the data is worth the expense. (It's not their data, it's probably not worth the expense.)

If the card is broken in any fashion and it happens to be found, it's highly unlikely that someone would go to much effort to read the data off of it unless, of course, you are a "person of interest" (to the police, national security, corporate exec, etc.) who might have data that you are trying to hide and that agency is actively tracking the card and looking for it to pursue a conviction, gather surveillance data, etc.

i.e. If you're a "regular citizen", it's very unlikely that anyone would attempt or be interested in the data they find on a random SD card somewhere. As a matter of fact, the rule is that you do not insert unknown data storage media of any sort (memory card, USB drive, hard drive) into a computer system, as "bad actors" have been known to intentionally drop them in the hopes of spreading malware of various sorts.