Some breaks can get crowded, but generally if you show respect you’ll be greeted with nothing but a friendly welcome. Wildlife is all of the friendly variety, and whilst Guinness hangovers are serve at times, they aren’t really that dangerous.
The main thing to worry about is the power of the waves and the reef. Whilst not sharp like coral, the barnacle encrusted slabs of rock are pretty harsh to connect with especially when a wave is breaking on top of you. It’s the number one danger, and you should always be respectful of the power of the ocean.