Gulls will drown anything given half a chance. Every year at the Strait of Gibraltar at migration times the local yellow-legged gulls will gang up on anything they get their eyes on; short-toed eagles, booted eagles, sparrowhawks, etc, etc, etc and try to drive them into the water. A couple of years ago I watched a black stork coming in and being harrassed all the way until it reached the Spanish shore.
Last May we spotted this griffon vulture that had been driven into the sea just short of landfall. When we spotted it, it was flapping weakly in the sea, but luckily for it the outcrop of rock in the photo was only about 50 metres away from it and it managed to reach it and scramble out of the water. It stood on he rock, wings spread for about 45 minutes, constantly harrassed by gulls, until it dried out enough to fly the last couple of hundred metres to land, passing low over my head before flopping exhausted onto the hillside where it rested for another hour.
Only a few minutes before we spotted it we'd been watching another griffon which wasn't so lucky. It was flapping in the water about a quarter of a mile offshore and without a handy outcrop to assist it, it drowned.