Sinister Seaweed?
Aquatic Encounters with Megaflora
George Laking
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Dungeons & Dragons - - Dragon magazine The Dragon #32

Land, sea and air—D&D offers excitement in every climate and
environment for the adventure-loving, treasure-seeking character!

Most adventures, however, are limited to dry land (dungeon-crawling
and the wilderness), since other areas are difficult to reach and
even more difficult in which to adventure. This is due primarily to the
fact that in the air the Pegasi, flying carpets and Potions of Flying/
Levitation are few and far between, while in the sea Potions of Water-
Breathing are of limited duration and effect (diving bells, submarines
and SCUBA gear not yet being invented).

To expand D&D adventures to the sea (at least in coastal waters),
the following “environment” has been deisgned by members of the
Mid-Columbia Wargaming Society of Richland, Washington.

Megaflora aquans (roughly translated ‘Giant Water Plant’) grows
abundantly in all seas and oceans, although it flourishes best in warm,
tropical waters. Growing in stands of 20-200 individual plants in depths
ranging from 60-200 feet, Megaflora resembles nothing more than
especially massive, dry-land conifers (spruce, fir and the like).

The boles of Megaflora often reach or exceed 7-12 feet in diameter,
particularly in stands growing at depths in excess of 100 feet. Unlike
conifers, they have no bark but only a tough, fibrous outer shell
protecting the soft, spongy pith. Cutting living Megaflora is very similar
to slicing dry balsa. Dead specimens will be extremely dry—out of
water—and very brittle (one or two blows with a mace will bring down
even the largest).

The branches of Megaflora are very numerous, forming a thick,
dense complex of interlacing, intertwining limbs. There is no other
foliage, as the limbs themselves act to absorb sunlight.

Like its smaller cousins, the common seaweed, Megaflora also
produces oxygen in the presence of sunlight. For this reason, no
specimen will grow to a depth greater than 200 feet, because all the
infrared rays necessary for photosynthesis are filtered out by seawater
at greater depths.

Because of the luxurious mat of branches and limbs, the oxygen
produced by Megaflora is often trapped in vast bubble domes within
the individual stand—the size of the bubble depending on the size of
the particular stand. The floor of the dome will be littered with a carpet
of dry, brittle limbs and twigs. This is due to the withering and dying of
the branches once exposed to oxygen (Megaflora is, after all, a water
plant!). For this reason, the interior of the dome will resemble a silent,
dimly lit, dry-land forest, with thick trunks reaching upward to the
“sky” and no undergrowth.

Bubble domes will be roughly circular in shape and located within
the center of the stand, although an extemely large stand (100-200
“trees”) could contain an odd-shaped bubble. As a rule of thumb, the
top of such a dome will not extend less than 20 feet from THE OCEAN
surface. To determine the actual height of the dome from THE OCEAN
floor, 2 formulas have been developed:

(1) For stands growing at depths between 60 and 100 feet, double
the number of plants found in the stand and divide by 10.

(2) For stands between 101-200 feet, quadruple the number of
plants and divide by 10.

These formulae will generate dome heights ranging from 4-40 feet,
depending on the depth and the number of Megaflora “trees” growing
together in a stand.

Besides the hazards invented by the DM for such an environment,
there are also natural dangers associated with Megaflora aquans:

While the stands represent no actual danger to coastal shipping,
there is a chance—the number of plants divided by ten and expressed
as a percentage—that a ship could become entrapped in the thick mat
of limbs at low tide. Such a ship will float free of the interwoven
branches by itself in 1-12 hours as the tide turns. The danger lies in the
creatures who may inhabit or use the stand for their own purposes:
giant eels, octopi, giant water spiders, sea ogres and the like. These
would be likely to notice and attack entrapped ships for food and/or
treasure!

Another danger—recognized by mariners and fishermen alike—is
the occasional Megaflora “blow.”

The Megaflora bubble domes are at best temporary structures,
depending for their existence on the dense mat of intertwining branches
to keep them submerged. Under normal circumstances, the interior
pressure forces out enough oxygen through the branches to maintain
the dome unchanged even as the plants produce more oxygen. In
some cases, however, the interlacing limbs act too efficiently as a cover
over the bubble and no gas escapes.

In that case, interior pressure builds up until-with a great thunderclap
and sudden rush of water-all or part (50% chance either way) of
the trapped oxygen bursts through the mat and escapes, throwing
shattered trunks and broken branches 20-200 feet into the air in a huge
fountain of water and foam. Ships trapped by a sudden “blow” will first
fall into the pit created by the outrushing gas, then to be slammed by
the inrushing walls of water and hurled skyward with other debris and
detritus—a very adequate reason for avoiding Megaflora stands when
possible!

If only part of the gas escapes (a minor “blow”), the interior of the
dome will shrink proportionately as the top of the bubble escapes.
Adventurers within such a dome will notice a sudden decrease in
pressure, followed by nosebleeds and popped ears (10% chance for
total loss of hearing in one or both ears due to ruptured eardrums).
There is also a 10% chance that a minor “blow” will sufficiently weaken
the remaining branches to allow the rest of the bubble to rise in 1-6
hours.

A “blown” stand will be characterized by a clear, peaceful lagoon
surrounded by walls of living Megaflora, growing quickly to replace the
damaged interior of the stand. Naturally, this lagoon will be the lair of
various sea monsters—all giant!—garding the scattered treasure of
ships lost in previous blows.

The sole warning that a stand is about to blow is the rising of the mat
above the ocean surface 1-6 hours before the blow occurs. A fierce
surface storm, weakening of the mat through rot and decay, or adventurers
hacking a passage through the branches to reach the dome’s
surface—all these could cause a stand to blow at the DM’s discretion.

A third danger lies in the fact that, at depths greater than 30 feet,
pure oxygen is extremely poisonous. Thus, any adventurer stands a
chance of absorbing a dangerously high amount of pure oxygen into
his bloodstream while in the bubble. This chance is equal to the depth
of the stand divided by ten and expressed as a percentage. For example,
a stand growing at 60 feet would have a 6%-per-hour critical threshold,
while one at 200 feet would be 20% per hour.

Checks should be made once per hour per character. Once it has
been determined that a character has exceeded his critical threshold,
no further checks need be made for that character so long as he
remains in the dome. However, upon leaving the bubble for the
surface, that character must make a saving throw vs. poison in order to
survive (failing to save means immediate death). Furthermore, for
every hour or part thereof that the character tarries beyond threshold,
he receives a cumulative -1 on his saving throw!

Finally—piling danger upon danger—pure oxygen is extremely
flammable—indeed, flammable to the point of being explosive! Thus,
only flameless light sources (magical or phosphorescent) are possible in
Megaflora dungeons, since striking a flame or using fireballs would spell
immediate disaster.