My observations indicate that Bait Squid is the best bait to use in any water type besides lava. The reason for this is that bait squid don't return baits and so for a higher level fisher who never looses bait, and never accumulates bait, a much higher percentage of their catches yield trophy fish. Considering how rare sharks have been historically, not enough data could be collected to know if there was an actual increased chance to catch a shark with a blood leech over a bait squid or herring or even a minnow - and due to unique way that bait squids interact with the fishing loot table(s) it is hard to make an argument that even if the blood leeches grant a 0.5% better chance of getting a shark in loot table, that the elimination of bait catches doesn't amount to a more significant bonus. Now that young version of fish are flooding the market, I am hoping that bait will get a pass (if it hasn't already) to look at what baits are beneficial for what types of water. Also, for the health of the fishing economy, I think since the rare trophy fish are so much more available, once baits become a greater factor in catching, perhaps circumstances can exist to where a trophy version of a rare fish always consumes the bait used and possibly significantly increasing the bait recovery level needed to achieve 0% bait loss - or some other means of ensuring high level fishers need bait on occasion too.