Shoulder strengthening exercises?

Hi, 5 month old diver here. I just tried front fall in from the 5 m platform and am sore in the neck and shoulders for two days now. I was squeezing my head between my arms for dear life to avoid hitting my head on the water, and did my best to keep the squeeze/alignment as I went under water. But it seems that I should probably strengthen my shoulders so that I am better equipped to brace against the impact. Anyone have any good strengthening exercises which would help with this? I'm not talking about warmup exercises (e.g., arm circles) or stretches.