Thrown spears, probably not. The lip of the Colosseum is fairly high. Arrows, maybe.

I hate to say it but, these were probably crazy to watch (loss and amusement of human life and rights aside).

The naval games were particularly bloody - gladiator games only sometimes ended in death, naval games had massive casualties, sometimes reaching into the thousands, which is part of the reason why they were a rare ‘treat’, usually using criminals condemned to death rather than trained gladiators.

The gladiator games in general were wildly popular with the Roman population, but it was noted by Romans that, by the queasiness of foreign visitors to the games, that it was something of an acquired taste.

Of course, the Romans took this as proof of their own superiority, since ‘even’ Roman women and children enjoyed the games! What weak-hearted barbarians!