*under water*
00-11 - footsteps
12 - SWS land movement
13 - base defense
14 - ajax launcher
15 - dup launcher
16 - dart rifle hit
17 - dart pistol hit
18 - gas cannon
19 - dart rifle fire
20 - dart pistol fire
21 - gas cannon hit
22 - hydrojet hit
23 - hydrojet / torpedo fire
24 - gas cannon fire
25 - alien built-in ranged fire (eg. deep one)
26 - electric sound (melee / disruptor launcher)
27 - craft destroyed
28 - ufo crashes
29 - explosion
30 - explosion
31 - sonic/gauss hit
32 - ?
33 - gauss cannon fire
34 - gauss rifle fire
35 - gauss pistol fire
36 - sonic cannon fire
37 - sonic rifle fire
38 - sonic pistol fire
39 - ?
40 - ?
41 - thermal shok / grenade throw?
42 - throw
43 - MC
44 - item place
45 - reload
46 - electric door
47 - regular door
48 - underwater ambience

*above water* (+49)
49-60 - footsteps
61 - SWS land movement
...
95 - electric door
96 - regular door

*generic*
97 - pwt launcher
98 - ui window popup
99 - human death
100 - ?
101 - aquatoid death
102 - gilman death
103 - tentaculat death
104 - lobsterman death
105 - tasoth death
106 - calcinite death
107 - deep one death
108 - biodrone / sws death
109 - triscene death
110 - hallucinoid death
111 - xarquid death
112-116 - alien movement (115=tentaculat)
117 - flying movement
118 - ?
119 - ?
120 - ui button press
121 - ?
122 - land ambience