Only about 4 Bubbleberries spawned on that, not sufficient to get there and back. If this isn't an old bug repeating, it might be worth changing the chances of the berries spawning on each Weed container. Character was Meroim Brushe, the other PC Mary Steel was also in the party. No errors were in the log.
Happened to me a while ago. I drowned.
It happened though, as i was soloing.
Bug can't be fixed, it's a result of players with lag opening the weeds and not properly closing them this causes them to be "stuck open" which means nothing can spawn in them until the server resets. Theres absolutely no way to fix it.
It is possible to complete this quest without bubbleberries, although it can be a near thing.
While it's been a long time since I've done this quest, you can beat it without using very many. Much like diving repeatedly to collect seashells. It takes a while, but I used to finish the quest with tons of extra bubbleberries for personal use.
I actually thought the purpose was to gather bubbleberries for future use.
I haven't done it in several months, so this post may not apply.
I'm guessing it does, though.