Easiest way is to map the serpent sightings, and prepare a trap at the nearby coast by just digging a little pond that is seperated from the open sea by a little bit of earth that you leave in place to act as a barrier and then just drag the serpent inside with the harpoon. Map the trap too to find it easily.
New Serpents should spawn at the same spot that you mapped so you can reuse your trap.

it's also possible to ram into the serpent with your ship after harpooning it which can result in the serpent getting stuck on your ship, it will stop attacking and you can park the ship in shallow waters to get all the scales. It might look very scary because the serpent head might be on top of you while you are steering the ship but it doesn't attack, apparently the Serpent only fights stuff that is in the water and it has to be in the water itself to attack anything.

Some stamina food can help a lot when dragging a serpent with the harpoon.
Also Serpents tend to spawn around those Ocean "Islands".

Easiest way is to just use a mod to change auto pickup distance, double it from 2 to 4 and just make sure you kill them close enough to you. Since I did this, never had an issue with serpent loot again. Sure you can drag them to shore but F all that. The devs plan on dealing with it eventually, either by allowing items to float or by adding diving to the game, the latter seems more likely. There is currently a mod that adds diving to the game already.

Yes I'm afraid that is intentional. The serpent meat always used to float, whilst the scales sank to the bottom (even prior to the update) and yes they do expect you to drag the serpent on to land using the harpoon. Admitedly a bit of a hassle to do in singleplayer, but possible with preperation (as in having a high stamina bar whilst slowly dragging the serpent behind you, to make sure you don't deplete said stamina until the last bit at the shore). The Frostner usually does short work with serpents (one or two hits), but that is pretty much considered an endgame/late midgame weapon. The shallow pool suggestion mentioned above sounds good though.

This flows with how game progression is designed (you have to do x before y). Go find the kraken (floating islands) and harvest what you need for a harpoon.

As far as I know: All buyancies are kinda realistic.

Creatures and boats destroyed in the water cause some of the loot or materials to drop or sink depending on weight. Examples of floating material include wood and trophies; while nails, pelts, coins, etc. sink to the bottom and can become unreachable. Player deaths in the Ocean biome generate a floating headstone, and boat inventory is stored in a floating crate.

Source: https://valheim.fandom.com/wiki/Ocean

They need to add the ability to dive. That way I'd probably actually level the mostly unnecessary swim skill.

I've lost about 15 troll hides so far in a new game, after they roll into the water.

Originally posted by jamesc70:

They need to add the ability to dive. That way I'd probably actually level the mostly unnecessary swim skill.

I've lost about 15 troll hides so far in a new game, after they roll into the water.

What works for me is building a ladder high above it and jump on the loot I need. Works for shallow and medium depth.

If you pull him to a Black Forest you can even drag him near a Troll and the Troll will kill it for you.

If you time it right you should be able to jump at it as it dies and collect most of the stuff that sinks.

Because not everything is this game has to be trivial AF. Serpents are not a threat if you have upgraded fine wood bow and some fire arrows. Later in game they melt with few frost arrows. Harpoon it and drag it to shore and beat to death with what ever you like. Easy. Easier with a friend.

Harpoon serpents is one of the few reasons you need coop.

Don't really need Coop even, tbh. As long as it's pretty close to the ship, the Stamina drain is negligible.