Fine fish offcuts and the recent sweep-up changes
For those looking to stack fine fish offcuts for hunter/herblore a combination of the recent sweep-up updates make it fast and afk.
It is now very easy to quickly stack up large amounts of shark lure from aerial fishing and then use them up on the sailing shark fishing spot that never moves north of karamja. You can stay there indefinitely just cutting the sharks on your raft.
It is a fairly fast alternative to deep sea trawling for ironmen who have not setup a boat for the purpose (which you definitely should) or those who would rather spend their trawling time to keep the more useful fish.
For those unaware sailing has created a very consistent way to train herblore on an ironman without having to farm seed/herb drops or doing endless farming contracts through armadyl brews. Both the "herb" and secondary for the potion can be gathered consistenty.
Umbral frags for growing coral are gathered from thieving Reinforced Chests which can be spam clicked to stack them up easily. The bottleneck for rainbow crabs for me has been fine fish offcuts which are somewhat slow or high intensity to gather.
Edit: discussion has brought up the idea of putting a chum station on the raft as cutting the sharks with a knife is rather slow.