if CLIENT then

    local blur = Material("pp/blurscreen")

    hook.Add("RenderScreenspaceEffects", "water", function()
        local ply = LocalPlayer()

        if not ply:IsFlying() or ply ~= me then
            if ply.water_snd then ply.water_snd:Stop() ply.water_snd = nil ply:SetDSP(0) end
        return end

        if not ply.water_snd then
            ply.water_snd = CreateSound(LocalPlayer(), "ambient/water/underwater.wav")
        elseif not ply.water_snd:IsPlaying() then
            ply.water_snd = nil
        end

        ply.water_snd:PlayEx(1, 30)
        -- lowpass filter
        ply:SetDSP(31)

        local W = ScrW()
        local H = ScrH()

        surface.SetMaterial(blur)
        surface.SetDrawColor(255, 255, 255, 255)

        for i = 0.33, 2, 0.33 do
            blur:SetFloat("$blur", 2 * i)
            blur:Recompute()
            render.UpdateScreenEffectTexture()
            surface.DrawTexturedRect(0, 0, W, H)
        end
    end)

    local function draw_fog()
        local ply = LocalPlayer()
        if not ply:IsFlying() or ply ~= me then return end

        render.SetFogZ(5)
        render.FogMode(1)
        render.FogStart(0)
        render.FogEnd(256)
        render.FogMaxDensity(0.999)

        local c = render.GetLightColor(ply:EyePos())

        c.r = c.r * 0.6
        c.g = c.g * 1
        c.b = c.b * 2

        c = c * 255

        render.FogColor(c.r, c.g, c.b)

        return true
    end

    hook.Add("SetupSkyboxFog", "water", function()
        return draw_fog()
    end)

    hook.Add("SetupWorldFog", "water", function()
        return draw_fog()
    end)
end

hook.Add("Move", "water", function(ply)
    if not ply:IsFlying() or ply ~= me then return end
    local vel = ply:GetVelocity()
        vel.z = vel.z * 3
    ply:SetVelocity(vel * -0.1)
end)